Ask an Property Solicitor. Get an Answer ASAP.
There is no reason why an estate agent acting as a mortgage broker cannot put all your sources of income down and then leave it to the lender to decide whether that income is reliable enough for the purposes of the mortgage.
The decision as to whether you get the mortgage on the basis of that income comes down to the lender. There is no legal reason why it should or should not be taken into account.
Can I clarify anything for you?
Please rate the service positive. It is an important part of the process by which experts get paid.
We can still exchange emails if anything needs clarification.