Hi oasis, yes, do ask your friend for the builder. That really would be the best thing.
Once the architect has been to see you, and between you you know exactly what you want it could take him a couple of weeks to draw up the plans and then submit them to the council.
You then get a reply from the council with a pink piece of paper you have to display on your fence for 21 days, during which anyone can object to your plans etc.
After 21 days if no-one has objected the coucil probably then take a couple more weeks to say all is OK and basically give you the go ahead to start building.
Our latest 2 story extension - bigger kitchen, extra bedroom and cloakroom took approx 10 weeks.
This will obviously depend on your building company/how many people they have on the job etc.
And if you can get your builder to include on your quote all the extras - like tiling, plumbing, electrics etc. - rather than you trying to organise it with individual workmen, it will be a lot easier.
Hope that's of help.