Why not fit them yourself!
Use a suitable sized truck tyre as a workbench, don stout boots and walk the tyre on. A plentiful supply of tyre soap or talcum powder and it's not as hard as you'd think. If you do have to use a lever, just make sure you don't pinch the tube.
I don't know if I'd get away with it at high speeds, but I have no balance weights on the Avons on my car. Feels good to at least 65, car's not been faster.
In the UK, any tyre place will give you a used truck tyre as that way they don't have to pay for disposal.
