Hello! Planning an extension

[Bob77]

Hi all, I have just registered and been browsing the forum - looks like plenty of useful info to be had here. 
 

I am in the early stages of planning an extension to my three-bed end of terrace house which is rapidly running out of space with two growing kids. Budget and planners permitting, I am looking at a two-storey side extension (to add a fourth bedroom and an ensuite to our existing bedroom upstairs, and enlarge the kitchen and add a second room downstairs), plus a single storey extension to the rear. 
 

I am also interested in finding out about heating systems. Although there is a gas supply here it has never been connected and the current heating is a an all-electric mishmash that has been added over the years, with storage heaters and electric underfloor heating, and costs a fortune considering the size of the house. 
 

The cheapest thing would probably be to connect the gas and put in a traditional central heating system, but I would like to do something a bit greener if the initial outlay was not prohibitive. 
 

Anyway I will post up some floor plans soon to get some ideas.