STOP!!!
Sit down, have a cup of tea and remember this isn't personal!
There are so many things wrong with your approach and understanding I don't know where to begin, so I'll just go through your statement in order.
PIC Hours - you don't need to be on your own, but you shouldn't have too much guidance either. The whole point is that you build experience making decisions by yourself so having a CPL sat next to you kind of defeats the object. You learn by getting yourself into situations, then getting yourself out again, building confidence. It is Not about your standard of flying improving (It will not!) - generally your flying deteriorates and your decision making/confidence improves. That's why you do the CPL course - it is designed to bring your flying back up to standard. The truth is the CPL test is basically just another PPL test and nothing to worry about if you know the area.
Time building to 200h while studying. You fell for the oldest trick in the book: concentrating on getting the CPL first. Big mistake. BIG mistake financially. I don't know how many hours you have but I strongly advise you to have your ATPLs finished by the 100 hour mark. Even if that means slowing down or stopping flying. If you follow your plan - yes, you'll get a CPL at 200 hours, but then you'll have to pay another £10-15k for an IR. If you get the IR first, it counts as hour building which means it only costs about £2k (you're paying for the plane anyway)
Don't try to second guess what hours you'll need for a job. 200 is the minimum so that should be your target for the licence, after that by all means get extra hours, but don't expect to have any kind of advantage. An airline (generally) only cares about one thing: multi crew time. To them a 200 hour pilot, a 250 hour pilot and a 1000 hour pilot are all basically the same. If anything, having too many hours can be considered detrimental, and believe it or not people have got jobs only after they removed hours from their CV! Sure, there are a few airlines that have advertised for 300 hours, but that's generally to whittle the applications down. Get the license first and worry about finding a job later by networking, but that's another story.
Far more important to the airlines that hire low experience guys is how recently you got your licence. If you're modular, they don't care about your PPL or even CPL: they want to know when you passed your MEIR and MCC (the more recently the better!)
So help yourself - by NOT doing them. Get a SEIR, get a SE CPL and wait until the market is favourable - then get your MEIR and MCC. You'll not only save money, you'll save the ATPL exams. Eventually when you write your CV you can legitimately put down that you got your MEIR last month and your MCC last week. You'll be competing against guys who got theirs 2 years ago and are rusty, they might have even paid to do a second MCC just to get back up to speed.
Getting a job in aviation is like surfing. A lot of waiting for the perfect wave. Mid 30s is certainly not too late, unless you think a 30 year career isn't long enough? The shortage will come, they always do. All you can do is be on the board, facing the right way and ready to paddle.