Sharing my experience and would recommend staying away from Currys deals which need Topcashback for them to make sense.
£800 HP laptop bought in July 2020 which admittedly was an ok price but not great. There was 20% cashback on laptops with AMD processors at the time so would end up being a reasonable amount back and make the deal very good.
I've just had the cashback track at just over 13 months later. I've been chasing it through TCB customer service about twice a month and looks like Currys just don't respond. Yes I'm happy I got it in the end, no I do not think it should have taken that long.