If you have used the housebuilder's preferred/recommended/suggested or one from their list, I doubt you will have any say or control over the process at all. Some buyers get caught by the legal fees paid or cash back or stamp duty deals on condition you use the builder's solicitor. Be sure though it is the absolute worst thing any new home buyer can do.
Assuming you have you own solicitor, one that has no connection at all with the housebuilder, I am sure they could make changes to the contract and send it back unsigned until the amendments are agreed.
You might like to quote the
Consumer Protection from Unfair Trading Regulations 2008 It is wholly unreasonable to prevent a new homebuyer from inspecting, or having their professional inspect on their behalf, their new home before completing on the purchase.
The APPG EBE Inquiry Report recommended it should be a mandatory right and I am currently working with several MPs to get this and other benefits for new homebuyers introduced.