Anybody on here fitted 265 / 50 / 20' tyres on their 20' wheels.
I'm aware the size should be 275/40/20 but would like to increase the height of the tyre because the vehicle for numorous reasons needs a little more ground clearance whilst normal suspension height selected.
What are my tyre options without resorting to wheel changes.?

Just curious but more height in normal suspension setting, for more ground clearance? For what reasons? 2003 BMW M5 - 5 Litres of V8 Optimax Slurping Goodness in Carbon Black

2013 SDV6 HSE Black Edition- Orkney Grey with Ebony & Ivory. LR Facelift RAI, Genuine G4 Expedition Rack, 4x Warn SBD-160 Spotlights, Warn 9.5XPS Winch, Mantec Underbody Protection and Sump Guard, Full Easy Lift Suspension Module, LR Light Guards, Light Force HTX230 Hybrid spotlights, 18” Compomotive PD1881 on 265/65/18 BF Goodrich KO2, ARB fridge, TuffTrek awning 😎

That will just give it a higher centre of gravity for normal driving

You can get the same result with the OBD Tool if it’s higher ride height you need. 2012 5.0 SC AB
Mods:
TPMS
Genuine LR DRLs
Remote Boot close from key fob
2016 Discovery 4 Mirrors AKA RRS2
2014 L405 Surround Camera retro fit (WIP)
2013 RRS Dual View Screen fit (Complete)
2016 LR4 RSE
2014 LR4 Homelink
2016 FFRR Electrochromatic Wing Mirror Glass

70 plate Focus ST (Current)
1942 VEP Ford GPW Jeep (Willys) (Current)
1943 Whites M16 Halftrack (Current)
16 plate Eurofighter Typhoon, 2 x Eurojet engines with 20,000lbs thrust each. 1380mph

Signal drop out...double post. 2012 5.0 SC AB
Mods:
TPMS
Genuine LR DRLs
Remote Boot close from key fob
2016 Discovery 4 Mirrors AKA RRS2
2014 L405 Surround Camera retro fit (WIP)
2013 RRS Dual View Screen fit (Complete)
2016 LR4 RSE
2014 LR4 Homelink
2016 FFRR Electrochromatic Wing Mirror Glass

70 plate Focus ST (Current)
1942 VEP Ford GPW Jeep (Willys) (Current)
1943 Whites M16 Halftrack (Current)
16 plate Eurofighter Typhoon, 2 x Eurojet engines with 20,000lbs thrust each. 1380mph

Not exactly what you asked, but I'm running on 255/55R20, very comfortable ride.  --
2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear
2015 Range Rover Sport Supercharged V8 HSE Dynamic



Defender Puma Workshop Manual: https://bit.ly/2zZ1en9
Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO
Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ

274/45/20 is not an unusual choice. That will give you a little over an inch bigger diameter.  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Have that size on mine

Not sure what you need the extra 20mm radius for, but if you need more clearance then get an IID Tool and raise the suspension to your liking, +15/20mm up to you.

If it's better off road traction and a softer ride, taking into account the higher center of gravity then you can go a number of different routes.

I've ran 275/45R20s, 285/50R20s and currently run 275/55R20s all are no issue except the current 275/55R20 Mastercraft AXT which required I raise the suspension a further 15mm to avoid any rubbing issues.

The increased CoG doesn't bother me, even though the word "Sport" is in the Range's name it's not designed to be a sports car and therefore don't drive it as such....

Hope that helps a little, but, without knowing the reasons behind the need for the increased ground clearance difficult to give more detailed advise.

Cheers

Guy 2006 RRS S/C CONSTANTLY under modification...
1994 RRC 4.2l not LSE sadly gone but not forgotten
LR Defender 300Tdi - affectionately know as "The Black Beast"