United Kingdom
Single malt whisky miniature is worth adding because it feels like something you actually noticed while travelling through United Kingdom, rather than a generic souvenir. For alcohol, I would only bring this back if it is sealed properly and comfortably within the UK allowance; otherwise it is better as a UK-buy link. The ideal version is modestly priced, not too bulky, and good enough that you would buy it again even without the holiday memory.
United Kingdom
This is exactly the sort of thing I like bringing back from United Kingdom: small enough to fit in a bag, but specific enough to remind you where you bought it. Biscuits and dry breads are good because they survive the journey and are easy to share at work or with family. It is also the kind of thing you can talk about when someone asks what you brought back, because there is usually a little story attached to where you found it.
United Kingdom
I would put English breakfast tea on the list for United Kingdom because it is the kind of thing that feels useful once you are home, not just another airport purchase. It is a good one because people can try it slowly at home, and it makes a nicer gift than a mug with a place name printed on it. The reason it works is that it gives you a quick reminder of the trip without needing to keep a fragile ornament safe forever.
United Kingdom
When I think of an easy, crowd-pleasing thing to bring back from United Kingdom, marmalade jar is a good pick because it does not need much explanation when you hand it over. The best version is usually the sealed jar, tin or packet from a normal supermarket, spice stall or food hall, not the most expensive tourist version. I would rate it higher when it is locally made, clearly labelled and easy to use at home, and lower when it is just tourist packaging.