It was about 2-3 years before I started making friends, but that was mostly because I didn't put myself out there as much as I should have. Also, my hubby is really shy & didn't have an extensive social circle for us to start with - plus maybe it is a man thing, but he really doesn't keep in touch with his old friends that much (spread throughout the country) - like even those who attended or were invited to our wedding which was mostly his family & friends (since we married here).
Anyway, it did take getting into the workplace in a job that I am okay with before I started making more friends - but as someone else mentioned, my work friends are sort of more superficial & revolve around work - lunches together during a work day, and the odd night out for drinks or dinner after work.
Surprisingly, I've met most of my local friends that DH & I both see regularly through this here website! The majority of which are British/American couples like us. It's not because I especially set out wanting to meet Americans per se (or want to limit myself to that - no way!), but maybe it's just that we have that shared cross-cultural experience in common now. Anyway, that's how it worked out.
We are both busy with our jobs & doing up our house, etc...so we don't get to see our friends as often as we'd like sometimes (maybe that's a 'getting older' thing - I don't know?)...but now I feel like my social life is just as rich and full (if not more so!) than it ever was in the US.
Oh also I've met and am friendly with a number of my neighbours - some of whom I've met on the bus to/from work in city centre. I go out for dinner every now & again with a couple of older (than me) neighbour ladies & that's fun too! I find people here in Yorkshire, northern England & Scotland, in general to be actually quite friendly & outgoing on the whole. I can't speak for the south because I've not lived or traveled around that much down there.