I trained with RUSTA. All their staff are ex-RAF or ex-army flying personnel. Maybe not the cheapest but in my opinion the best. It may boil down to if there is a course run by any organisation that is close to where you live or if you are prepared to travel. This might include having to seek overnight accommodation, which will increase the cost even more.
I have seen that there are now companies offering on-line courses. No idea about the quality of these on-line courses but I guess at the end of the day, you get the same qualification as every other company.
Just a word of advice for you, before you start laying down your hard earned. Do you have customers ready to go once you attain your PFCO? Have you got some kind of business plan? Or do you just think that you'll get your PFCO and the customers will just start rolling in? 90% of people who attain a PFCO don't renew it after their first year. There are more costs to this type of venture than you might realise. The UK market is pretty saturated with PFCO holders now. Add to that, the fact that big video production and TV companies pretty much dominate the aerial video market. To these companies, having someone with a PFCO is just another tool in their box. They have budgets and assets that a sole operator can only dream about. If you want to get a PFCO on the back of a promise of just a few jobs, I'd think seriously about it before you start laying down the readies. Really, the costs just keep on coming and it's starting to get even more expensive each year when you have to renew your PFCO with the CAA. I did 3 years and then got out. It's just my opinion, but it's more work and expense than you might realise.