Extension - Leasehold Administration Fees

Lillil

We live in a leasehold house and as far as I can see from my reading of the lease we need the freeholder's approval to build an extension to the property. We have paid a £111 "non refundable request fee" and have now received a form to complete which seems to indicate that this approval may end up costing a further £1,440 made up of the freeholder's management company fee of £360, solicitors fees of £480 and a surveyors fee of £600. The extension is modest, doesn't need planning permission, with an estimated build cost of £15,000 so paying 10% of this in charges appears excessive. Other than buying the freehold is there a way to avoid these charges and can the management company charge £111 just to send us a form to complete?