Realistically once India (& to a lesser extent Malaya) the entire enterprise of Empire was untenable. However with that being said I can see a world where Malta, Singapore, Suez (if we called the US bluff) are kept for strategic reasons & more of the Caribbean colonies are kept after the failure of the West Indies federation
Of other places mentioned as “trade ports” I don’t particularly see the feasibility of Aden being retained as a sort of Anglo-Djibouti given the armed resistance that occurred during the 50s/60s. Mombasa however is an interesting idea that could be plausible if Britain intended to continue to use Africa as its breadbasket, becoming a Goa like enclave in east Africa where grain & animal produce are exported - but imo its only going to happen if somewhere along the line it’s separate from Kenya in the same way Singapore is from Malaya - perhaps the nominal treaty of coastal land leased from the Sultan of Zanzibar is invoked as being separate to the colony to Kenya, & in the negotiations for Kenyan independence Mombasa is “retained” by the British over the rest of the coast
One place that hasn’t been mentioned is Guyana, somewhere which could easily be retained in the same way France does French Guiana if one of the following occurs:
1) Guyanese oil/gas reserves are discovered in the late 50’s/early 60’s - & it becomes a Caribbean version of north sea oil propping up the economy
2) Prior to the independence vote, Venezuela invades the Essequibo region & are defeated by a mixed force of British regulars. Concern about the risk of future invasion without British support causes a postponed vote to go in favour of maintaining British rule
I might actually write a timeline where some of these are kept actually. Some interesting butterflies could occur - though I suspect it’ll just be another cold-war timeline where Britain doesn’t consistently make the wrong decision at every hurdle
Regardless the retention of any of the colonies mentioned wholly reliant on a precedent set (likely by Malta who actually voted in favour of integrating into the UK in 1956) of joining the UK in a similar way to how France operates her “overseas departments”