I want to do a deal but worried they won't let me before the case is heard - mainly driven by the fact that they're making me attend court.
But your case is already going to be heard in court as the deal can only be agreed there. Whether you are there or not depends on the court. As I explained in my post on 5th January, some courts allow this deal to be conducted under the "Single Justice" procedure (which you cannot attend) whilst others will require your attendance at a hearing in the normal Magistrates' Court.
As far as I am aware there have been no cases on this forum that we know of where the deal has been declined. On its predecessor (Pepipoo) there was only one from a very large number over many years. That was where the defendant was somewhat uncivil to the prosecutor, who felt disinclined to assist him by agreeing to the deal. If I am correct, he finished up with nine points for his trouble.
You simply need to proceed as advised on here. In the (extremely) unlikely event that your offer is declined, you will have to decide whether or not to maintain a not guilty plea to the FtP charge. As above, your chances of success with that, on the basis that you posted a response but have no proof of that, is fairly slim to say the least. But I would not lose too much sleep over it because I can say with a fair degree of certainty that your offer will not be declined.