Thanks for the advice, i considered using the 2x 30KW, but lack of space prevented this. I've decided to go for an Ideal evomax, and an S-Plan plus system.
Diamondgas, I've been a gas engineer for 17 years, and untill two years ago was a mechanical engineer site foreman for a large domestic/commercial company running up to £500K contracts, two years ago I set up my own business. After working for 16 hours yesterday and then having to do this quote my brain was frazzled and I was after some confirmation (or not!) before emailing it over!
Gasmarc, I did a church last year, boiler, up to 4" iron pipework and underfloor heating, it was cold when I started, hot when I finished, I think God loves me!