I'd say if you can afford it and you really want it, go for it! There is no point in having lifelong regrets, working your ass off at your garage while longingly staring at the aircraft flying overhead.
Obviously you are aware you could end up splashing £100K (or whatever it is these days) at the Bristow Academy and end up with nothing, but that is a risk that any self-funder takes - it sounds like you have sufficient financial backup to absorb that.
Another benefit of the BA is that Bristow will interview you for an FO position (if they are recruiting at the time) whereas if you had done your training elsewhere the hour requirements are much higher.
Recruitment in the North Sea seems to be proceeding at a rate of knots at the moment and has been for the last year, I just wonder how much longer for? There are people here far more qualified than I to speculate on that, I'm sure!