Borrowing more on Halifax mortgage

Hi all

I took out a Halifax mortgage last August. The loan-to-value was 80%.

Since purchasing the property we have added a second floor and three bedrooms (it was a bungalow) and carried out a complete refurbishment. I estimate our loan-to-value is now more like 65 or 70%.

I have a couple of expensive unsecured loans and credit cards and would like to pay them off by adding to my mortgage.

I notice Halifax require you to have had the mortgage for six months, so I've just become eligible. I just want to know the process for this - will they carry out another full credit search, require bank statements/wage slips etc.? i.e. will it be another cumbersome/long process or is it more straightforward and will they just internally check?

Obviously the house will need to be re-valued and that's fine. My main worry is that, although I have NEVER missed a payment and have a clean credit file, my "% of credit being used" is about 90% so I guess that might worry them a bit.

Appreciate any advice/input! Thanks!