Ok, last night I found my car had been clamped. I phoned the clampers and they wanted £141 to remove it. Plus they weren't going to come out last night to remove it. 
So they agreed to remove it at 8am this morning. Anyhow after many phone calls it was 10am and they still hadn't arrived.
So, I thought I'd take a better look at the clamp. Fortunately beetles are pretty easy to work on, so I removed the ball joint and suspension and the clamp slipped right off.
So far I haven't contacted the clampers. (PS this is a 'private' clamping firm, not council. I would never consider doing this if it was).
They've tried calling me obviously not found me where they left me, but I havent replied yet. They've sent me a text saying they 'know where I live' and they're staking out the M2. Which is nowhere near where I live.
The notice they left on my window has a PO box and address, so I'm going to send the clamp back 1st class recorded delivery to them, completely undamaged by being removed. However I feel I should should text them back to let them know.
Am I legally withing my rights to do this?

So they agreed to remove it at 8am this morning. Anyhow after many phone calls it was 10am and they still hadn't arrived.
So, I thought I'd take a better look at the clamp. Fortunately beetles are pretty easy to work on, so I removed the ball joint and suspension and the clamp slipped right off.

So far I haven't contacted the clampers. (PS this is a 'private' clamping firm, not council. I would never consider doing this if it was).
They've tried calling me obviously not found me where they left me, but I havent replied yet. They've sent me a text saying they 'know where I live' and they're staking out the M2. Which is nowhere near where I live.

The notice they left on my window has a PO box and address, so I'm going to send the clamp back 1st class recorded delivery to them, completely undamaged by being removed. However I feel I should should text them back to let them know.
Am I legally withing my rights to do this?