How much more expanding foam are you going to be using for other jobs? If you're using an expanding foam gun, you need a gun, cleaner, and cartridge(s). If its just this job buy an all in one as it'll be £7 instead of £40. If you follow the instructions you can keep the foam for at least 3m (this is how long my has lasted so far, Idk if it'll be OK for longer)
Get a decent caulk/sealant gun: https://www.screwfix.com/p/no-nonsense-heavy-duty-sealant-applicator-gun/136fr
How much more expanding foam are you going to be using for other jobs? If you're using an expanding foam gun, you need a gun, cleaner, and cartridge(s). If its just this job buy an all in one as it'll be £7 instead of £40. If you follow the instructions you can keep the foam for at least 3m (this is how long my has lasted so far, Idk if it'll be OK for longer)