My previous Octavia Estate 110 TDI (Elegance) has been written off.

Apart from Auto-Trader and Flea-Bay, how do I find a replacement.

I guess the insurance will give me 1 or 2 weeks before they want the rental car back. (I hope)

I have recently changed jobs, so no longer do 25k+ miles a year, going to be more like 5k.

Don't want to spend more than about

I would say supermarkets, but for those prices you are looking at the used car lots for a larger car.

Get down BCA for a look about, get a feel for how things work, build your confidence up, and bag a bargain!!!