Inside layout is crucial, as they vary so much, depending on the number and ages of people using them and their lifestyle. Some things will be essential for some folk but endlessly annoying for others.
Twin axle will open some doors for you but close others. You can have a lot more weight and more stability with towing, but you need a heavier, less fuel-economic car to pull it, plus twice as many tyres in contact with the road will also reduce fuel consumption - as well as obviously costing twice as much to replace. On the other hand, if you have a blow-out whilst travelling, it's much easier to come to safer and more controlled stop with 3 wheels than with just 1. Also, some caravan sites won't allow twin axles, or will arbitrarily charge more per night for them, if they do.
Also, if good internet (4G/5G) connectivity and/or TV are important to you, it might be worth allocating some of your budget to a good auto-tuning satellite dish and/or roof-top wifi router (to be used with a data SIM).
As with cars, several of the big makes are owned by the same companies, so there isn't necessarily that much to choose between them. I've heard of Hobby (German) being solidly-made - plus they tend to be slightly wider than some others. Not always by a lot, but an extra 3-6 inches in width can make a big difference to how roomy they feel inside. Adria (Slovenian) are also solidly made and a slightly less well-known brand, so you may get a bit more for your money. Just make sure that, if you do go for a European-made one, it has the door on the 'correct' side for the UK.