Jimbo,
First off welcome to the wonderful world of aviation. At 27 you are no way too old.
Ok first off if you are totally serious that commercial is for you, I would go get a class one medical so that you do not waste any time and money if you are not fit enough to fly. This is done at the CAA in Gatwick and will set you back 400 squid!
Next you need to get a PPL, this will probably cost in the region of 3000-4000 squid. It will give you around 50ish hours and also your first license for a single engine aircraft.
After this you can do 2 things: Begin doing your ATPL theory exams, either via distance learning or at a full time approved school. Cost around 2000 for distance learnng or 4000-5000 for full time.
Next plan, to get your CPL, for this you need 150 hours total time to be able to begin the course.The CPL allows you to get paid for flying and is neccessary.Cost wise, your looking at 4000-5000ish i think.
After this is done, you could go 2 ways: first off you can get your Instrument Rating, this is the killer you will get 55 hours flying time, of which some may be in a fixed base sim.It is done usually on a twin which bumps up the course cost somewhere around 10000. Secondly you can do your FI ( Flight Instructor Rating) allowing you to go and teach at schools throughout the UK, this is a great way of getting hours and experience, as most airlines may not look at you until you have around 1000 hours!
Finally all going well you need to do your MCC (Multi Crew Co-operation) basically working as a pilot in command for 10 hours and then the other way around for 10 hours. This will be between 2000 and 4000, again rough cost.
All that completed you should end up with about 250ish hours and can then be employed by any airline!
If you are looking at flying schools to go to, then use the search facility at the top of the page, just type in something like ATPL Training and you should get a fair whack of different schools.
I see you are from Hull, i would advise a visit to Humberside INT'l and call in at AAA (Triple A) Flying School, they can tell you what you do and don't need.
Hope it works out for you, see you in the sky!