i would recommend a worcester 30 si,10.8 ltrs of hot water per min,91% efficient,they come pre wired so you only need a plug,plumb center are doing a deal,boiler,flue and prog for less than £800 + vat,you will need a filling link also which is less than £10!any other boiler i have evr fitted(at customers request)and they have been trouble,steer clear of alpha,ferroli or keston.