Hi, Slimming World can be *really* cheap and, if you don't already have the info about it, it's reasonably easy to find most of it online or by asking people on here. Alternatively, you can buy the starter packs on ebay for around £10 or so.
Other than that, in the past, I've simply upped my daily excercise and cut right down/out sugar, fats and alcohol. It works very well
Group fitness classes (before 5pm Mon-Fri, after 1pm weekends)
Fitness gyms** (before 5pm Mon-Fri, after 1pm weekends)
Fitness gym inductions (times as above)
Swimming at all times during casual public sessions