I did it about 8 weeks ago but can't comment on how successful it has been as the CAA still have not issued the licence! - but thats another story.
If you are a resonably competent single-pilot IFR driver then there should be no reason why you can't get up to speed and do the 170A test inside the 15 hours. Remember 10 hours can be on an FNPTII rather than the aircraft which substantially cuts down the cost.
Email me if you want a recommendation for a good FTO or any more info.