If you want personal experience you might be better requesting Private Messages. Most people who have done it the way you're planning are too paranoid to post on Pprune in case they are identified and it affects their job prospects.
From my experience Severn/Bristow is certainly flexible and have good instructors. If they are busy be aware they will take as much business as they can to meet their targets. This is understandable but it will effect your training. If they are quiet then you get the their full attention. I choose them because they were the best value for money and flexible and I got exactly what I paid for. There was of course the naive idea that it would help me get a job with Bristow. Don't fall for that one, especially when they are trying not to let anyone go at the moment. From what I have seen Bond are more structured but if they are busy and are limited with aircraft then your training could be delayed. If I was going to do it again and wasn't worried about money I would pick the least busy school with perhaps Bond edging slightly ahead given that people have been hired by them recently. You should also factor renewal after 12 months because unfortunately you still might not have a job. The type rating really doesn't play into it that much with only 150hrs I'm afraid.
I heard that one of Severn's instructors recently left for StarSpeed to set up an IR school. It might be worth checking this new school out too. He was a very experienced pilot, a good instructor and really knew what he was talking about. An instructor who really cares about his students. And don't forget Helicopter Services in High Wycombe which is respected industry wide. I don't think it matters where your IR comes from, it is about whether there is a need for pilots and your face fits. In fact, in some cases it might be better to choose an independent school.
A bit of thread drift but correct me if I'm wrong, the helicopter industry really is about putting yourself out there and hoping for some good fortune. If you happen to be in front of the right person on the right day when they are in a good mood, your odds increase dramatically! However, a few days later and you're forgotten. If you call them up to reminder them who you are but catch them at the wrong time then your a marked man with absolutely no chance!
I guess one thing you still have some money in the bank. You really need to start thinking about alternates. Don't be so focused and in such a hurry to get out on the North Sea to fly back and forth to the Rigs! If you position yourself correctly you will have 30 more years of flying to do that. It has been really difficult the last 2 years and unfortunately there are no immediate signs things will improve. I certainly don't envy you, focus on increasing your odds and best of luck!
By the way well said both times by Hands_on123!
PT