mortage for putting two flats back to one house

Hi there, I am a first time buyer.I have 12% deposit. house price is £90K.a four bed Victorian terrace that is currently converted to two flats and registered as such.The structure appears untouched with the internals to make two flats simply stud walls & internal doors.The property still only has one front door & one rear door.I would like to put it back to one dwelling upon purchase... What problems might I encounter,if any from a mortgage application - would they require one mortgage or two? are lenders more skeptical to lend in such cases?

I have saved a long time for this so want to get it right! any help appreciated! regards - Rob