dont bother about the RAF flying or anything like that if you intend to go commercial as ive been told that the hours dont count to your civilian future.
option 3 is the best and the way i did it.
finish a degree but if you find somthing other that avaiation that your intrested in go for that as otherwise your options are restricted. if i were you i would not bother about flying until you finish university. only reason is if your only doing one of two lessons a month you are likely to take more hours to finish as you get rusty between lessons.
finish your ppl then go back into university for ATPLs. they are hard but you should be able to work weekends during the whole thing (including university and ppl). ive been working throughout my studying and had no problems other than never having time to myself! you may also want to be doing some hours during the weekends as well to stay current.
once your done with your ATPLs finish your hours building. ofcourse there is no problem working through that.
when it comes to the CPL, ME, IR its best to make sure you have enough money in the bank to compleate them one at a time without taking a break as otherwise again you will prob need more hours.