Ask for a breakdown from the LA.
The fees for building regulations have changed and some items are now works specific. The LA will change per sepecific item, i.e a rear extension and a loft extension as two separate items even though the work may be undertaken at the same time and therefore less time consuming as two separate projects.
If there are two work items / fees and you’re going to carry out the works together then discuss it with the council and you may be intitled to a 50% rebate on the lower fee. I’ve been told it’s discretionary but managed to obtain a rebate in a similar situation early in the year.