Loft Conversion SE London recommendations?

[conkerpods]

Hi,can anyone recommend a loft conversion company that they have used,and any to avoid please?
Also,cost.....We have 40k but I'm thinking we will probably need about 50k all together so wondering if my mortgage company will let me borrow any extra 10k.
Is 50k realistic?We have a 1930's mid terrace and we would like a bedroom and bathroom with a dorma.
Any other tips or advice greatfully received