Speaking from experience:
Firstly, You will only get the reduction
-if you pass all the modules within the timeframe (3 Years) and
-your attendance is above a certain threshold (over 90%)
-YOU GET 20 WEEKS OF EXPERIENCE WHILST STUDYING.
It is very unlikely that a part-147 organisation will accept you for work experience in the UK. So you should ensure you can get this otherwise you will need 5 years experience.
If you don't meet any of the critirea, The College will refuse you the Course completion Cetificate that you need to reduce the experience time and you will be left with only the modules (assuming you passed)
Then you will only need to find a mechnic job to get OJT (On the Job Training, basically means working, paid or unpaid)
There is alot of competition for mechnic jobs from people who have graduated from the BSc (with or without) so chances of getting a job in the UK are very slim. Mechanic jobs pay around 17-25K.
Provided you work for 2 or 5 years (depending if you get the course certificate or not) you will have a basic B1 licence. This is useless in itself as you need to do a type course to be an engineer. Type Training is usually provided by the company (if you are lucky) when needed and can last upto 3-6 months. or you can pay for your own training for upto £5-10k.
Only then you can be a B1 licenced Engineer, earning around 30-40K.
Don't be drawn into it by the glossy marketing literature of the uni/college and promises of a licence in 5 years. 5years is the minimum if everything goes your way and you find a job.
Also keep in mind that the BSc itself is almost worth zero in the maintenance industry without the licence modules.
You would be better off getting an apprenticeship with an employer if you really want to do the practical jobs. You could have an A licence, with the experience and no debt.
Or do the BEng and get a degree thats worth alot more and will get you into design/planning maintenance etc.
Sorry for the long post but you should have the facts in front of you before deciding.
Having said that don't be put off if you have already made you mind up.