It doesn't need to take 18 months, you'd be lucky to get an integrated course done that fast. That's the beauty of a modular course, you can make it last as long as you need it to.
Don't underestimate how long your hours building will take, especially if you plan on doing it all in the UK. There's no reason you can't take your time for your PPL and drag it out over 12-18 months, enjoy the journey. As you've already mentioned, there isn't any rush to finish, so don't rush to finish.