Same as us, so for that reason i would say let's diversificate.Going back the the RAF next manned platfrom, BAe is far more integrated in the USA than europe and possibly BREXIT will exacerbate this. Whilst a european UCAV is likely to have a UK contribution, isn't more likely that we will continue to follow the US considering we are more in sync with their timeframe for the next platfrom the France or especially Germany?
Going again with the US would be investing to much in them, at least for us not Anglosaxons like you, plus they just elected Trump wild card and we don't know how will be the situation in 20 years.
At the same time do you see the french and the germans skipping completely the 5th generation, land the 6th, with the French attitude ("we are willing to allow the UK to enter in the project...") and german spending that in 2022 will be less than now? I don't.
Being in a similar situation i would say, lets wait, lets focus on the unmanned sector for now or consider the Japanese or Turk option. If Russians are going to collaborate with the Turks then it would be better if it is us, at least we could cut the logistic support in case the situation goes sour.
https://www.defensenews.com/industry/te ... -interest/