I generally go Parcelforce48 collected is about £9. Probably cheaper out there but I’ve had bad experiences with everyone apart from Parcelforce. Rims generally don’t need much packaging either, I usually use a worn out tyre to protect.
I always box them with bubble wrap, even with parcel force. Old office tile light boxes are ideal size.
Parcel force is my weapon of choice too. But remember they can / will reject parcels with pallet wrap / loose plastic on the outside as it can get caught in their machinery ....its in their terms.....so boxes it is.