EnvyFlies I shouldn't lose anymore sleep over worrying about this. You have the correct GCSEs and probably more importantly work related experience in the industry.
I was an ATPL theory instructor for 25 years and in my experience other than the rare exception degrees & A-levels made little difference to the end result as it mostly about motivation & staying power.
However GCSE level maths/physics & problem solving are important. For physics go and revise the gas laws and moments. For maths you need to able to transpose/cross-multiple formula, interpolate tables of data, work percentages (forward & backwards), use graphs and understand their scale. In General Navigation & Flight Planning you need to be able to do distance/speed/time/fuel problems & preferably with a gross-error check answer before you hit the calculator.
Rather than going getting A-levels (which from a content point of view will be of little value) before your ATPLs I should get yourself current and fast on what I stated above. Most ATPL course providers offer a maths/physics refresher as a pre-requisite or get some private GCSE revision tuition. On a positive note one of my former private students had almost exactly the same background as you do, 6 years later he is now an FO with Jet2 back at the base where he used to work the ramp.
You can do A-levels or an Open University degree later if you wish.
Best of luck (PM if you wish).