What do you tend to do as leisure activities and what would you like to do? Taking up a new hobby would be a good way of meeting people.
I'm a scuba diver and BSAC club member. We have a regular club training night, have regular days out to dive in lakes and the sea and go on holiday together to dive - I've made quite a few friends this way and we even do non diving days and nights out together too. You could do this sort of stuff with lots of other hobbies, cycling, running, hiking, book groups, craft clubs, all sorts.
If you don't want to go abroad or on a 'proper' holiday, can you build up to it?
Go on some local days out and treat your locality like a tourist would. Look at the local tourist information website (www.visityourtown.com) or go in person and choose a few things to do and do them.
Go for a day out at the coast or to a nearby big city you haven't seen enough of. Or book a night's accomodation and go early in the morning to get two days there?
A PPs driving tour and Premier Inn break upthread sounded quite lovely.
Or a cruise, that's often a good choice for a solo traveller and you can mix with people or be alone as much as you like.