Of course if ya said what you wanted the rope/strap for. you might have got a bit more advice. is it just for towing?? If so any cheap towing rope/strap will do. Be aware of the following.
Reg 86 Road Vehicles (Con and Use) Regs 1986
Where a trailer is attached to the vehicle in front solely by means of a rop or chain, the distance between the trailer and that vehicle :
1. Shall not exceed 1.5 metres unless the rope or chain is made clearly visible
2. Shall not exceed 4.5 metres in any case.
If you're looking for a recovery strap/rope for offroad use see my previous advice regarding lifting strops. If you pefer a rope 10tonne would be the preferred size.