Isn't there often a debate about how the armed forces want kit that works (e.g. from the US) rather than debugging some homegrown alternative? Isn't the price of 'homegrown' that you have to put up with all the problems till there's enough money to sort them out?
If we went to at a UK company wouldn’t be able to meet the need anyway - we buy in penny packets spread over years and the company facilities and staff are set up to do the same - take NLAW as an example.
Assuming we don’t expect to go to war without US support, then we can draw on their reserves - as we did during the Falklands war for AIM-9Ls, fuel etc.