Right I'm looking at a mk 1 octavia vrs in the morning 54 plate with full service history, 1 owner and very we'll looked after.

My only worry is the engine has done 135k miles is this a problem as the car has been well looked after or should I worry ?

I wouldn't worry too much. it will be due it's second cam belt replacement at 140k unless it's been done already. Check for smoke under acceleration and the normal stuff

And see what receipts there are.  Suspension if not changed will probably need doing.  Check the guide at the top of the forum.

that mileage isn't a problem at all

Drive it and see how it feels.

that mileage isn't a problem at all

I agree. The engines are tough as old boots. Its the shocks/springs that are a weak part.Noisy bearings also as mines needed two at around 100k. Looked after, which it sounds like it has, the mk1 Octavia is a very tough car. Good luck!

Keep an eye out for any rust too.  Crouch down and check the sills.

Mines on 140k.drives sweet as a nut. As previously mentioned check for rust, breather pipes and the normal stuff in the guide.