Before starting, I also run all my spending and expenses, through the best cashback website, Topcashback - join them via link https://www.topcashback.co.uk/ref/exclusivebonus for a joining bonus!
Note: when spending is a requirement of an offer e.g. 'spend £5' - I just top up my Amazon account, this counts as a transaction, and the credit on your Amazon account is valid for 10 years, so it's as good as cash if you shop there!