Replace sime friendly format 80,which boiler is best on a budget?

[mangoman]

Hello,my old sime combi boiler needs replacing and i need some advice on the replacement please.My selections so far are the glow worm flexicom 24cx,potterton perfoma 24he,ariston e combi 24ff i want to keep the total price including flue etc under £750.I could stretch my budget a little if the boiler is worth the extra dosh.
Cheers.