TBH, even back in the 1980s it was difficult to see what sort of operation we would have conducted with F117s of our own that wouldn't also have involved allied operations with the USA. GW1 was a good example of that being so. We couldn't have used them in a Falklands scenario, and probably wouldn't have needed them either. Any kind of European conflict would have been a NATO affair.
Acquiring F117s would have been a nice demonstration of "The Special Relationship", and with Thatcher and Reagan getting on very well it's not wholly surprising that it was considered. What is moderately intersting is the timing. The DoD only confirmed the existence of the F117 in 1988, yet the offer was apparently made in 1986, two years earlier. Certainly, reading Ben Rich's book, one gets the impression that the F117 was the most closely guarded manned weapons system in the US inventory at the time, the holiest of holies, for use only when it really really matters. Perhaps the fact that Rich had a British father, and Alan Brown (Rich's programme manager) was British, also had something to do with it too.