Best way to get some building work done

[peaceful1]

I have a small terraced house in the suburbs of SW london. I want to get the ground floor refurbished and the side return filled in to make a larger kitchen. I need the ground floor replumbing and rewiring and the side return filling in which would involve putting in i think two supporting beams. I joined the green concierge service who said they would put me in touch with reputable and suitably green builders but sent over a building firm who said dont bother with an architect, we will draw up the plans as they are simple and gave a quote of �100,000 for the job (drawing the plans and doing the work). The side return is around 5 foot wide and 14 foot long just to give an idea of the scope of the extension. Now i work full time but earn the average wage so would not be able to finance �100,000 for the work but do urgently need it doing as the property is now in a very poor state and i have been saving for ever to get it done. I wanted to ask several questions. -Do architecture students ever want/need to do projects for their qualifications and is this a possible way of getting some sort of help with planning the extension at a price i can afford. -What is the best way of finding a good builder to start getting quotes for the work? And yes i know asking people for someone they recommend would be good but all i get told is "I wish i knew a good builder" -What sort of ball park figure would you expect to pay for the rewiring and replumbing of the ground floor (which will be a large living room and a kitchen which will remain in their current position but the kitchen will be larger due to the side return extension) and the extension. I appreciate no one can say a rock solid price as this will depend on many things but can anyone give an idea so i can get a sense of how realistic it is to get this done? I really am struggling to know how to go forward with this and would appreciate any advice anyone can give. Many thanks