Hunting for a decent used BMW with proper luxury credentials? Chances are you're only considering a 3 Series or 5 Series, but what if we told you that you could step up to a 7 Series for only a little extra cash?

A 3 Series or 5 Series estate won't cost much less than a comparable 7 Series saloon: a 2018 730d with 52,000 miles is stonking value at £20k, for example, while a 530d of similar vintage and condition could nudge £17k.

It feels a good bit more special, too. Open the driver's door and you will see a badge on the B-pillar proclaiming a 'carbon core'. It's not a full, i8-style tub but a steel and CFRP structure that, together with a mostly aluminium body, keeps rigidity up and weight down (to as low as 1755kg) - which is great news for dynamics and efficiency.

Admittedly the interior could have been a bit jazzier, but liberal use of leather and metal throughout still bolster the 7 Series' premium cachet-and it has aged well too.

Even in short-wheelbase guise the 7 Series is a whopping 5.1m long, and it's commensurately capacious inside, with a boot that rivals many estates' for outright capacity, at 515 litres, and a mile of rear leg room.

The long-wheelbase car (badged L) is 140mm longer, and all of that is felt in the rear seats. It is even more spacious than the equivalent stretched Mercedes-Benz S-Class.

Two options are key to maximising the richness of the passenger experience: the Executive Package and the Rear Seat Comfort Package. You will often find them specified together, in which case look forward to heated and massaging 'comfort seats', multimedia screens and a tablet to control just about everything you might need from the back, from the ferocity of your massage to the channel of the digital television - which can also be used to browse the web.

On the road, the biggest weakness of the 7 Series is exposed. It's no S-Class, that's for sure, producing more wind, road and suspension noise and serving a less cosseting ride. It's still deeply impressive, but the disparity is big enough to notice.

However, if you're not being chauffeured, you might prefer the extra poise offered by the BMW's stiffer suspension. Cars with Active Steering have a rear axle that turns against the fronts at low speeds for better agility or with them on the motorway to improve stability.

Most sixth-generation 7 Series (codenamed G11 or G12 in L form) are 730d (261bhp) or 740d (315bhp) variants, which is handy because this is a cruiser that's best served with a diesel engine. The 3.0-litre 'B57' turbo straight six is a quiet and torquey lump, and owners reckon 45mpg is achievable, making for a range of more than 800 miles.

The 2.0-litre four-cylinder 725d (228bhp) is very rare and hardly any more efficient, while the quad-turbocharged straight-six 750d (395bhp) never made it to the UK.

Petrols are less common but worth seeking out if you don't do big mileages. The V8 750i (444bhp) and V12 M760i (610bhp) are effortlessly quick but have the running costs to match; the 'B58' six was available on its own but more commonly sold in conjunction with a battery and electric motor in the plug-in hybrid 745e, which allowed for a real-world electric range of 25 miles.

The G11 may not have the bling to match today's G70, but if you're after a luxurious BMW, it could be the most sensible option of all.

An owner's view

"My short-wheelbase 7 Series is surprisingly brilliant to drive on UK roads. I stuck to the 18in alloys and paired them with the upgraded Adaptive Drive dampers, and I have no qualms with the ride. The 315bhp, 500lb ft 740d is fabulously fast while returning 40mpg, it even makes a reasonable noise and the Active Steering really works at keeping the big girl manoeuvrable without changing the BMW feel of the dynamics at speed." Tony Cole

Buyer beware...

Engine: Watch out for coolant leaks, hot running or a blown thermostat. These issues are usually caused by poor-quality plastic pipes. We recommend replacing them with aftermarket metal items.

Gearbox: ZF's widely used eight-speed automatic torque-converter handles shifting work for all engines. It has a great reputation and needs a service only every five years or 50,000 miles to keep it smooth.

Electrics: Failing seat occupancy sensors throw up airbag warnings. Air-conditioning evaporators have failed - an expensive job that requires the removal of the dash. Some seat massage buttons have got stuck in the off position or stopped working entirely, with BMW dealers having to replace the unit to fix the issue.

Suspension: The standard air suspension is starting to fail on the oldest cars out there. BMW will charge you £4000 to renew it all round, but a specialist should be able to do it for as little as £1000. The compressor costs another £2000 from BMW or half that from a specialist.

Drivetrain: BMW's xDrive four-wheel drive system has a good reputation, but without a service every four years or 50,000 miles the differentials will wear.

Also worth knowing

A 2019 facelift introduced a controversial new face featuring massive kidney grilles, while extra sound-deadening measures improved refinement. The slow-selling 2.0-litre 740e PHEV was swapped for the 3.0-litre 745e, boosting electric range slightly in the process.

Trims were either the luxury-focused Exclusive or more common M Sport with cosmetic upgrades. Both are well equipped but buyers had to dip into the options list to level up their cars with everything from night vision and laser lights to Adaptive Drive, which greatly improves the ride.

All engine options are ULEZ-compliant and cars registered after 1 April 2017 that are more than five years old are just £195 per year to tax.

How much to spend

£11,000-£15,999: The lower end of this budget will buy you something with 200,000 miles, but find a no-expense-spared service history and you're looking at a potential bargain.

£16,000-£24,999: Pre-facelift cars with anywhere from 100,000 miles to less than 50,000. Most are diesels.

£25,000-£29,999: Wide choice of facelifted cars, V8 petrols and later plug-in hybrids.

£30,000-£45,000: V12s and last-of-the-line models. Remember, the current 7 Series can't be had in pure-ICE form.