The rules for ramp angles and gates ironically relate to vehicles that have ramps. There is a loophole that means if the vehicle doesn't have ramps then the rule doesn't apply, however they have to see the vehicle as being suitable for carrying the livestock.
If it can be hosed out, livestock separated from driver compartment and sheep can be lifted out then it ought to be ok, but can't guarantee it. Trouble is those commercials will be heavy to lift out!
I would ask the abbatoir, and I would take all of them and put the meat in the freezer. Each sheep will only take up one box for the Shetlands maybe a box and a bit for the commercials. Box is about 2 foot by 12-18 inches.
Towing wise if you passed post 97 you likely wouldn't be able to take them without doing a trailer test as you are limited I think to 750kg and that's trailer and load of sheep, everything, basically you can only take a bit of rubbish down to the tip in a small box trailer without the test.