I have little to no experience with London radio, I spend most of time chatting with cabbies when I’m in a black cab. What I miss is seeing pub, pret, pub, pret, pub, pret :)

https://radiotoday.co.uk/2020/02/rajar-q4-2019-london-and-na... suggests Radio 4, Radio 2, Capital FM, in that order

Kiss FM or Capital FM. I can still hear the jingle for capital FM! or perhaps LBC 97.3