I am assuming for the moment that they had Judgment for the £700 plus costs.
If that is the case then you are in difficulty.
You have made an admission of £700
You can not, therefore, apply to set aside the CCJ for £700 because you made an admission.
You can only set aside if you have a defence to the claim.
If you make an admission they are entitled to enter a CCJ for the admitted sum
If they filed the CCJ for the £700 then your application will fail
This is because its for the admitted sum.
Can I clarify anything for you about this today, please?
If you need anything further I am available for a follow up at no extra cost.