Bank Switches are very lucrative, upto £250 a time. Have a donor bank account ready (easy to do from the bank you are with) set up 2 DDs, I use PayPal and an empty credit card.
I use receipt apps: Zipzero, shoppix and storewards. The last 2 give PayPal or Amazon vouchers, not a lot but get £2-5 most months. Zipzero pays out to your bills, so I use this for my Gas / Elec or council tax, although they are having cashflow issues at the moment and havent paid out in 3months.
Cashback credit cards, debit cards and reward bank accounts. Get paid for every £1 you spend. If you are going to spend it anyway, might as well get paid for it. My platinum Amex pays me £200pa, really useful as it is deducted from my Jan statement so is knocked off my Xmas spending.
Every penny you are not currently using should be in an interest bearing account, easy access savings so can transfer it if needed in a second.
Store loyalty cards, I have them all. I'd say the only 2 that really pay off are Nectar and Lidl but becoming more needed are the dual pricing is coming into most chains. I keep them all on an app, Stocard so no hassle keeping hold of physical cards. Even keep my library cards on there.
The main thing to buy "only what you need" as cheaply as possible. Get to know if Amazon is cheaper than B&M for that shampoo you like. I buy stickered food and freeze. Yesterday, I picked up 3 packs of co op deluxe Cumberland sausages that were reduced, separated them and froze them, I'll bag them up today. Easy to airfry only a few frozen sausages at a time, no waste.