Still use RS and Farnell quite a bit, but prices are getting much worse with them both over time. And RS is getting particularly bad with order sizes, the minimum quantity on items keeps seeming to rise. used to be you could often get just 5 of something*, now for most things* you're looking at 20 minimum quantity. Farnell still does small quantity, but delivery is very pricey unless you bunch up about £50 of stuff over time before ordering.
I haven't used Mouser or Digikey so much, I don't know if you get import problems where border goons delay or try to thieve taxes on larger total value packages from them, because I do know they always ship direct from the USA where RS and Farnell ship from UK warehouses. Digikey has hugely expensive shipping if you order below the free delivery threshold, someone I know got charged £18 delivery for a single £4 part.
Rapid uses UK warehouses, and so does Pimoroni who are good for sensor breakout boards (adafruit, sparkfun...) and other more integrated parts (arduino, pi, kits of common parts...) but don't really have much selection of ICs and other lower level components.
*mid-range ICs, not the really pricecy things which are still sold as each or cheap passives that are always in 50s or 100s