Plusnet have quoted their contract:
22.2 We have no liability (whether in negligence or otherwise) for any loss not reasonably foreseeable by us when this Contract starts, nor any loss of opportunity, goodwill, reputation, business, revenue, profit, or savings you expected to make, wasted expenditure, data being lost or corrupted, loss or damage incurred by you as a result of third party claims or any indirect, special or consequential loss or damage howsoever caused.
I beleive my losses and costs could be reasonably forseen at the time of entering into the contract:

I believe it reasonable for Plusnet to foresee that, at the time of making the contract that:
1) Customers using their service will register domains with companies other than Plusnet and use those domains for the purpose of email.
2) Customers who need to change their domain(s) will incur cost and experience loss.
3) To prevent unsolicited email from arriving at a domain will require the domain to be changed.

This is all with CISAS right now.

Interestingly enough Plusnet Customer Services refused to give me my CISAS ID claiming I'd have to wait three months (as per CISAS guidelines) until I asked how the situation was going to change over the next three months and then they relented.

I agree Ni, it's not big bucks I'm asking for, but I still think I should be able to cover my costs fixing this, and then of course there's the matter of my beloved domain I will have to loose <sob!>

Steve