Change of tactic here, but if it's four tyres on rims, have you considered getting hold of a Euro-pallet and some wrap, then making use of an economy service on one of the pallet networks?? 99.9% of the waguns the haliers use will have tail lift and pump trucks because of the number of home addresses they do so getting it on and off ought not to be an issue.
I've done that before, I think the company I used belonged to TPN, and it came in at something like £40-50. Weight becomes a bit less of an issue then, as I have a feeling that four tyres on rims is going to be pretty close on 80KG. I'm currently driving a Pallet Track trunk vehicle every night, and frequently have pallets of LGV or agricultural tyres, etc, on so it's not uncommon.
Just a thought,
Jim.