To note.

It's very handy to have a trailer that can accommodate an 8x4 sheet internally...or at least that width. Just in case you need to shift timber sheets or anything like it.

Whilst it is of utterly no use to you in England, I've had one of these trailers for over 20 years, made by a local company. The newer design seems a little better too. Simple single axle, it'll take a 4ft sheet width wise ok, but not 8ft length, although door is easily removed, or just set sheets on top.
Plated at 500kgs capacity, so no issue with the unbraked rules etc etc

https://www.portertrailers-tractors....railer_004.jpg

https://www.portertrailers-tractors....id=17&Itemid=3

I've seen many big brand names that are of lesser quality than these, and often more money. I gave around £5-600 over 20 years ago. Money very well spent. Not sure how much they retail now for.