Ground Floor flat extension

[buttercup6]

I have just been granted permission for a ground floor flat extension. I have an architect who prepared all of the drawings and submitted the application on my behalf. Now I want to get some concrete quotations in from some building contractors - and the architect wants to charge me around 5,000GBP for the following activities:
Building Regulations compliance...............i.e all the information in order to satisfy the Council. Then construction / fit out information so that the contractor knows what to price for. Then a structural engineer who will need to work out the sizes of the steel supports and the concrete footings. This does not even include a party wall surveyor. Anyone help me understand whether the costs are realistic? Anyone completed a similar project? I love in West London so maybe there is a price inflation here.
Any advice is greatly appreciated.....thank you

We are very close to starting and a bit further on from you.

I would say that sounds a lot. Do you definitely need the architect to do all this or could you do it yourself?

Our costs have been structural drawings, £1000+Vat, building control £600+Vat, our architect will provide extra drawings to building control if required and will charge £800 + vat for this. Party wall is going to be over £2k+vat on it's own and that's with only one person to serve notice to. Do bear in mind the costs that can be associated with that as it took us by surprise. Also the cost of the license to alter which I presume you will need as you are in a flat?

We had a v clear idea of what we wanted in each room and our extension is fairly simple so we were able to write our own "shopping list" for each room that the builder could use, so I think that helps with pricing.

We are in SE London if that helps!