I use a product called Seafoam ( I don't know if you can get it in the UK). You add it to your fuel tank, I usually use 1/2 a small just under 1L can to 25L of fuel. I use it in everything My Mini, my truck, My Wife's car, my outboard, all the small engine garden tools and my emergency generator. It stabilizes Fuel and cleans jets & injectors.
I work in an Autoparts shop and we sell a ton of it we often sell out. Any stabilizer/injector cleaner should work. The carb cleaner is more for unsticking gummed up linkages than inside the carb.
We used to do it with Redex and brake fluid.
I did that years ago I don't know if it did anything except produce a whole lot of smoke.