If the house has changed shape since the flats plan was drawn, the title is defective and the bank may not lend.
A cross-lease means you own a share of the land with your neighbours and lease your flat from them all. The flats plan on the title shows the footprint of each building. If the footprint today does not match, because of a conservatory, a carport or an extension, the title is defective.
Defective is fixable, but it costs money and needs every neighbour's consent. The question is who pays and whether the bank will lend in the meantime.
A free 15-minute call with a property lawyer who only works with first home buyers.