Most insurance company's these days tend to re-place with an "Item" from one of the bigger well known stores, Rather than give you the cash to self purchase.
I think that with self-build it would be a good idea to keep receipts of all components bought. At least this will prove a replacement value. As for labour cost in self-build, I don't think they will cover this.
The only sure way is to make a phone call to your insurance company and ask. Also request a reply in writing, Mail/e-mail. J.