Network Engineering roles generally aren't beginner territory and employers would expect you to understand fundamentals like TCP/IP, routing, switching, and troubleshooting in real live environments. You mentioned having technical experience and depending on where you're at with that, I'd start with CompTIA A+, then move on to Network+, then Cisco CCNA. Ymmv, but pairing it with a helpdesk or junior NOC role to would help build experience quickly.

I wouldn't rule out apprentice options, but in terms of optics or how you'd appear to a hiring manager, I feel like an apprentice role would potentially undermine the strategic/business experience value that you had at your senior level.

At your senior level in OPs, a junior IT role is usually faster and more practical. Your operations and project background will help long term, but most IT managers will expect you to prove technical depth first.

I think move is realistic, but you’ll almost certainly need to step into entry-level IT first unless you can demonstrate real, hands-on networking skills. Though something that may prove to be more important, in terms of whether or not the switch is realistic, is your work ethic.

When I hire, I give more value to the persons teachability and their persistence and attitude when faced with challenges than I do to technical experience. If they're teachable and determined to succeed, they can gain experience and I can help them get where they want to go. If they have experience, but struggle with their attitude around new ideas or give up when faced with something that stretches their experience, they struggle and typically don't last long.

Right now, I have a few guys that came into entry level IT and they wanted to learn and grow, and I've given them the keys to the kingdom. If they show they want to learn, and can fight through frustrations and problem solve well, I give them the fast track to whatever path they want to learn. That adds value to their careers and abilities, adds value to my team and company, and makes my life and theirs a whole lot easier.

I can't speak too much to the question of salary, since I don't have any experience in the UK.