How do I bathroom / kitchen / extension? etc.

Questions re structural engineers: I am planning a kitchen reno which will include taking down a load-bearing wall between my kitchen/diner and enlarging a window opening such that it will need a small joist/new lintel. These feel like fairly straight forward structural alterations. I had been quoted £800+VAT from the surveyor I was obliged to commission to produce the report for the freeholder's approval. Having just met the surveyor I am very keen to find someone else to do the structural drawings. I have the following questions:

• What would be a reasonable price estimation for the drawings I require?
  
• Would you expect any 'aftercare' from a structural engineer? i.e. if a contractor required clarification about an aspect of the drawings or you wanted to query whether you could make a minor change?
  
• Would they provide any sort of a mediation service/'help' with getting building reg sign-off?
  
• Is there anything else I should be thinking of? Would some contractors provide this service? My assumption is I want the drawings in hand before getting contractors in to quote but happy to be put straight on this.
  
• Does anyone have a recommendation for a structural engineer who would cover SE London?
  
  

Any input, insight or recommendations greatly appreciated! Cheers