I find that even if I was not particularly motivated to get out on the bike, because I didn't have to go anywhere in particular, I start enjoying myself after about 20 minutes, and the memory of that enjoyment serves as motivation to go out the next time.
In other words, I don't need a reason to get out on the bike. Maybe you don't either...
Thanks for the tip. Looking at the stuff that's 25 miles away, my first thought is Stratford-upon-Avon, which I was planning to do a while back but didn't get round to it. Think I'll go for it.