Hi,
I can't help you with the Royal Signals Officer bit (I'm not/have never been one) but the area which you're interested is 'my bag' as it were.
The key thing to ask yourself is, what do you want to do? If a career in cyber security is something you want to crack open then I'd advise the following (I know a few folks who I've given this advice to and the concept broadly works but needs tailoring to your interests and strengths).
1) Work out what you want to do. Risk? Policy? Pen Testing? Crypto? Security Architecture? Hunt? Network design and hardening? Cloud? (Cloud is a biggy atm) Different skills, different working environments and career paths. If like me you started off fairly geeky you might want to build secure systems. Now I draw them on whiteboards and go hunting for threats in data. Have a think about what you want now and in the 3-5 year time frame. Try to play to your current strengths.
2) Do CISSP. Yes, everyone from, project managers, to spreadsheet wrangling risk professions to your Grannie probably has one but it means you'll turn up in the right CV searches.
Try not to do a course either to start with (they are absurdly expensive for what you get), get a book. As a comp-sci graduate I'd hope alot of it is not going to be mind bending stuff and do the practice tests, as many as you can. If you're still struggling then consider having some teach you how to take the test (as opposed the material, some CISSP 'trainers' are quite possible the worst infosec people I have ever seen)
3) Earnings and where do you live? Work out how much you need to earn and where you're happy to live. Consider the big names in consulting, many have Cyber components, PWC, KPMG, CGI, Leidos (LM's old consulting arm is here now), NCC. At the junior end they're hiring like crazy and hopefully being compsci and having some experience of the way the world works you're less of a chancer than some. If the numbers and location add up then happy days.
4) Learn in your spare time. If pen testing is your bag then CTF, doing more learning. My mate did
Offensive Security Certified Professional (OSCP) Certification, which is well regarded. He did loads of tournaments and loves it. If you want to build stuff gen up on your networks and the cloud. Grab an AWS account and start building and designing secure systems.
5) Volunteer. People here have done the JCU bit, but note that's
not LIAG. There are a number of pillars within JCU (as I understand it). I have a mate who's there, he's a programmer. You should call them and have a chat,
Working for JFC - Joint Forces Command - GOV.UK. Alternatively there is the NCA Specials programme,
National Crime Agency - NCA Specials, Hampshire and Gloucestershire Special Constabularies are also looking at schemes
DutySheet | Volunteering Blog | Cyber Specials: The story so far. Also, Herts. have a scheme
Hertfordshire Police - Special Constables. If you want to PM me, *roughly* where you live I might be able to point you in the direction of organisations for point 4.
Good Luck!
2PI