For what it's worth, when I joined my first commercial outfit (and this wasn't that many moons ago!), we were bonded for £15k, payable up front before commencing the type rating, albeit paid back in 36 monthly instalments...
The starting salary at that outfit plus the bond I paid was still significantly less (I'm talking greater than £10k) than the starting salary these new pilots would earn in their first year at BA.
Just my "two cents", but I don't see the problem with the £18k up front given the starting salary. A very controversial viewpoint I'm sure but sadly its the nature of the industry. I can't think of many another professions out there that requires you to pay up front to get the job.