T5-R or R buying advice / any for sale

I recently bought a regular 850 estate as a stop-gap but the more I look at it, the more I realise what an elegant design it is and think that I should get a T5-R or an R to keep longer term.

I'm a bit new to this, so any advice would be welcome, but specifically:

– what should I pay to get a T5-R or an R estate?

I'd like something reliable that's been looked after, though I'm less concerned about cosmetics, but mechanically needs to be sound. It's going to do some mileage, so high-milers are fine if the've been well maintained.

– Are modded ones with more power reliable or best avoided?

– Other than the odometers all failing at 150K (as far as I can tell), are there any other common faults?

– Does anyone know of any for sale?

Thanks in advance