I’m gonna point you guys over to my about page which has my cages listed ;p
There’s lots of big cages in the UK. We have the savic royal suite which you can get cheap on Zooplus. That’ll house up to 12 rats.
Little pet warehouse also has several large cages, including the aventura which is like the royal suite, but 30£ cheaper. It also has that blenheim cage but that’s only suitable for big males due to the super wide bar spacing. There are also a bunch of cages there comparable in size to the savic freddy and they’re cheaper, like this one which also comes with accessories for an additional fee.
There’s also of course, the Savic Freddy and the Savic Zeno 2. As well as the Ferplast Furet Plus and the Ferplast Jenny and if you’re really loaded and have lots of space, the Furet Tower.
There are also Marchioro cages, a lot of which have wide bar spacing unfortunately. The Sara 82c3 is huge but has wide bar spacing, so again, only suitable for adult males. If you can find a distributor, marchioro does a few good rat cages, it’s just hard to find a place that actually sells them anymore.
There’s the Liberta Explorer, but I don’t see the point in buying it when you can get the royal suite and the aventura much cheaper. Also from Libertra, the Riviera, comparable in size to a savic freddy, 1.5cm bar spacing, so should be suitable for females. The Liberta Discoverer is a massive rat cage (which comes in lots of colors).
If you feel like decorating a cage entirely from scratch, there’s also large bird cages like these available (I always recommend long bird cages over tall ones, rats are clumsy and could fall from tall cages). Just buy some savic plastic shelves, a bunch of hammocks, rope bridges, bendable perches etc and fill up all that space. It has narrow bar spacing, thankfully.
I actually feel like we have more selection for large rat cages here than the Americans do.
As for personal experience, I’ve owned multiple savic freddies, a ferplast jenny, a ferplast furet plus and a savic royal suite so if you ever want advice on those particular cages, feel free to ask. I would have to say, they are all amazing cages, Savic and Ferplast make exceptionally good quality products.
I hope that helps you and possibly some other British rat owners out there!