I run an exit node with an ISP who initially indicated they would not have a problem with Tor as long as I was transparent about what I was doing, and ran a sufficiently reduced exit policy. 

They have now sent me evidence of malicious traffic coming from the exit. I don't think they've had any 3rd party complaints about this traffic, but they have expressed various misgivings about Tor in general. They now also want me to consider running Snort IDS on the outgoing traffic.

I don't intend to monitor my traffic. But it occurs to me I don't know whether my ISP needs to be worried about it or not. The last one wasn't, so why them?

I've asked the EFF about the legal situation in the UK, who passed me to the Open Rights Group. They've not replied to my enquiry as of three weeks ago. 

So does anyone know of any reliable source of information on running Tor exits in the UK? What would happen if my ISP pressed me to monitor my traffic, and I refused on legal grounds? I'm not suggesting I actually do that, or that there are even any legal grounds to refuse. In fact right now I'm resigned to closing down the node if my ISP turns up the heat. They probably have me by the balls.

But I'm at least curious, and can't immediately find any information about things like public carrier status, or traffic monitoring conducted by people like me when it's done in the context of onion routing.

Thanks in advance for any help.