The N1 form is a form for filing county court action.
If you have a choice, it is always preferable to file using N1 at your local court. The two main disadvantages with MCOL are that your Particulars of Claim are limited to just 1080 characters with a maximum of 24 lines and you cannot attach the schedule of charges to your claim.
Both these drawbacks can create problems later on. The banks use these limitations of MCOL to assert, with some justification, that the claim has not been fully particularised.
Therefore you are strongly advised to file at your local court. It will be transferred here eventually anyway.
If you are on benefits, you may be eligible for exemption from court fees. You can only apply for this at your local court using form Ex160.
For detailed information about the N1 form see: Particulars Of Claim