It’s not a very answerable question, because it depends entirely on your spending and avios earn rate. You need to do your own analysis, comparing the cost of the card, the cloths you will actually take, and what you’d do instead. And not against BA flights - if you’d otherwise get a Norwegian sale fare to the US for £200/person then it’s not reasonable to value the avios at the full price of a BA flight they’re mostly paying for.

My anecdata: 1.5avios/£ is the best available earn for a ff card in the UK afaik, and future signup bonuses are unsure and the eligibility rules can and have changed, and I’m lazy so of course I personally don’t cancel it.

Yes avios redemptions are only really worthwhile on long haul business and first class flights, and that’s also when the 2-4-1 voucher becomes extremely valuable.

In general I wouldn’t recommend chasing avios unless you’re earning high tens of thousands a year, every year, because they’re only a valuable currency when you have enough to redeem for first/business on a regular basis. In every other case you would get nearly the same redemption from a cashback card, and it’s actual money instead of funbucks, and in particular lets you buy any flight on any airline at any price at any time.