I have somehow managed to acquire eleven wheels, but they are all 17". Can't see the point of going bigger

This is what is happening since the Land Rover design thinking Victoria Beckham and rappers from Miami, LA etc ... all exes, looks terrible XXXtreme Tuning  Yuri
(ARS) XE1UN, EA1HCZ

13 LR2 (FL2) HSE Lux SI4
Havana/Black
(Mexico)

08 LR2 (FL2) SE
Tambora/Black
(Mexico GONE)

05 DISCOVERY 3 G4 V8
Tangiers Orange/Black
(Spain)

13 RANGE ROVER SPORT HSE SDV6
Orkney Grey / Ebony (Black)
(Spain)

07 RANGE ROVER SPORT HSE TDV8
Java Black/Black
(Spain GONE)

02 DEFENDER 90 BLACK LE TD5
(Spain GONE)

09 VOLVO XC70 OCEAN RACE EDITION D5
Ocean Race Blue
(Spain)

I have 20" for the summer months on mine and 17" in the winter.

20" is fine, and to be honest, I've never felt that the ride has been degraded in to the bone-jarring harshness that seems so often portrayed. It quite simply is not as bad as people make out, or more to the point assume based on a notion that its a lower profile. Yes, 17" setup is a smoother / softer ride, but the 20" setup is still soft enough and smooth enough.

Also remember, that although a 45 tyre profile is considered low, the width of the tyre at 255 means that its still quite a lot of tyre wall depth to soak up bumps .... its just as much tyre wall depth as many small cars have, and cause its a larger rolling radius, will be smoother at going over the bumps.

What I will say is that I've jumped between an evoque 20" setup on 245/45 R20 tyres and my freelander 255/45 R20 and I would say that the slightly larger tyre felt better ... but how much of that can be attributed to the tyre versus the suspension setups between each I'm not sure.