London - kitchen side extensions

[satinpillowcase]

hello, have bog-standard victorian house, with side return. kitchen on different level to living room. want to connect the two rooms about five steps. don't think will extend kitchen into garden. will refurbish kitchen completely, put in wooden floor and maybe a small loo. want the side return to have glass roof and put in bifold or sliding glass doors.
realistically how much should i budget BEFORE architects fees for the work.
and how much are architects fees????
any advice gratefully received.