No problem - you're obviously genuine with your queries and not 'trolling'!
If you're going to OBA, you would certainly be well advised to complete your exams first as the pace of the course is quite demanding.
In the UK, you can take the exams at any FTO/RF which conducts PPL training - whereas in other countries you have to use an exam centre.
Reading the Trevor Thoms will give you an excellent start, and the PPL Confuser is useful for revision. As for the sequence of exams, I would suggest:
First, do Human Performance. It's pretty simple and will give you confidence in the exam system.
Then get the tedious Air Law and Communications (PPL) exams out of the way. Very dry subjects indeed - but a lot of 'air law' content is common to both. You may get a better deal doing the RT practical and Communications (PPL) exams in one package; also, the RT practical can only be done at certain Clubs and needs a specific RTF Examiner.
Then do Met, Navigation and Flight Perf and Planning. Many people find nav quite demanding, so practise as much as you can.
Finally, do Aircraft(General). This is probably one of the more interesting subjects; not difficult but a large syllabus!
You have to complete all the exams within 18 months; they are then valid for 2 years in which time you should do your flight training and apply for your licence.
Good luck - and sorry for all the rain we've been sending to Scandiwegia recently!