It does seem counterintuitive, but vouching ID is a safeguard against abuse because you can also order repeat meds and request access to your GP medical record through this account too. Worth the hassle to go through the hoops once to get set up.
Also, there are three main clinical systems in GP land and the online services available will be operated by whichever system your practice uses. They all now allow you to self-register for a limited online account which will just let you book appointments, but it depends on whether your surgery has activated this option or not. EMIS and INPS are the two biggest providers and cover ~75% of the UK, so it may be worth trying the ‘register without a letter from your practice’ option with both of their websites here or here. It will only work if your practice is on one of these systems and has allowed this functionality though.
Other than that, telephone appointments are good if your surgery will offer. It should make no odds to the GP - they just dial a number as opposed to calling you in from the waiting room.
Lastly, if it’s concerning meds and you’re really stuck there’s currently an ‘urgent medicine supply’ pilot going on where signed up pharmacies can dispense a short term supply of previously issued meds. This can be arranged through calling 111 and speaking to one of their pharmacists.