Sorry folks - should have posted an update earlier. Responded to the court with the following:
[cover letter with N1]
Thank you for returning the enclosed claim documentation and refunding my £120 fee.
I am re-sending these documents and returning your cheque, as I believe you are in error in your instruction that I will have to issue this claim in the Scottish Courts.
It is my understanding that The Civil Jurisdiction and Judgments Act 1982, as amended by the Civil Jurisdiction and Judgments Order 2001 applies to this case. In particular, Schedule 4 (paragraph

of the 1982 Act (as amended) provides that as a consumer, I can raise proceedings where the company is domiciled, in this case London where Abbey’s registered head office is seated.
Furthermore, It is my understanding that there is no clause in the terms and conditions with my contract with Abbey that confers exclusive jurisdiction.
In addition, if it is the case that exclusive jurisdiction applies, it is my position that this clause is an unfair term of contract in terms of UTCC Regulations 1999. Specifically paragraph 1(q) of Schedule 2.
In light of the above, please reconsider issuing this claim. I would also draw your attention to London County Court Case number 6CL01687 that I believe was issued under similar circumstances earlier this year.
If you decide you are still unable to issue this claim, please could you explain the reasons for your decision.
[snip]
The case no. quoted refers to Robertxc's claim.
My claim's now been successfully issued, already had 50% offer received and rejected, Allocation Questionnaire returned.
Waiting for court date now - still expecting a settlement but preparing for whatever Abbey tries next.
The Court address I've used is the Central London County Court:
Central London County Court
13-14 Park Crescent
London
W1N 4HT
Its all going like clockwork, and should do for you too. To avoid any unnecessary delay, I'd recommend a cover letter with your N1 quoting as much of the above as you want. This should ensure the claim is issued without a problem.
Hope this helps,
Tim.