Mildenhall sounds great - sadly I'm booked up that weekend.
I will have to come down to one of the next BHPC races at Hillingdon though - that's not too far from me.
I really like going to Hillingdon - although I haven't been as a rider for some years. Nice place to just wander around while the racing's going on. There are normally two sessions a year, at the beginning and end of the season, so you'll have to wait until October now, but that's enough time for you to finish your trike in time for a spin round the track there
As regards group riding, I've never been part of a cycling club so wouldn't know, but I'd imagine the reactions are pretty universal.
For me personally, I'm really not that bothered about being part of a group [that doesn't want me as a member], but the only downside to that, and it is a big one, is that if you want to make advances with fitness, then working with others is the way to go. Making progress alone is of course possible, but requires a shed load of discipline and motivation.
I could do with getting my arse well and truly whipped as well - I've had a project in 'gestation' for some 11 years. I've [tentatively] just started it! It wouldn't be so bad if those 11 years had been spent brain-storming some revolutionary idea, but no, it's just another recumbent that looks the same on paper as it did 11 years ago. I'm finding one minute I'm full of best intentions, next minute I'm sitting in a pub talking about my best intentions.
Hope you manage to finish the trike. Do it not for group riding, but for you... and your daughter