In my Non-NATS experience
1. No discount for PPL, not part of the 'syllabus
2. You need to begin training towards the Certification of your ADC Rating within 12 months of completeing the course. For an initial validation, you'll need to undergo a minimum of 180 hours of supervised training. You can only count 4 hours per day, so allowing for the appropriate rest days etc. this will take a minimum of 2-3 months, depending on the quality of you and your Instructors! You're then examined (practically and orally) by an CAA Examiner. If you pass, your then valid for 13 months. Many units (usually the larger and more complex) will have their own Training Plan and Examiners, but the same requirements apply.
3. Some Non-NATS Units will employ ADC only rated people with or without a view to future training, but you'll probably be at the bottom of the pay scale.
4. Additional Ratings will make you more of a commodity but it's a big investment with no guarantee of a return....and you'll still have no, or very little experience. Smaller Units will require you to have an APP rating but some of the larger regional airports employ ADC and APR only Rated staff.
5. Area is really only the domain of NATS...besides you don't actually get to see any aeroplanes...if you want to get out of the IT Ratrace, do you really want to work somewhere that looks like PC World?
6. Worth a try. Talk to Shearwater or ASTAC too. They probably have a better idea of the marketplace than most. There is a shortage, it will get worse and I can see units like having to look at recruitment from a different angle, like the one you're suggesting, in the future.
7. ATSA's get paid peanuts generally...but it's a great way to gain valuable experience.
8. YOU NEED TO GET A CAA CLASS ONE MEDICAL BEFORE YOU DO ANYTHING.
Hope this helps