Hi,
I feel your pain, it's frustrating.
That said, with a combination of lower expectations and more budget you can definitely pull out great stuff. You could check the youtube channel of Cuiv the lazy geek who is in Tokyo and got some impressive shots with his Rasa and appropriate filters in mono. Astrobiscuit is in London and also getting some good results.
I have no experience with mono and I use a 294 in Bortle 9 with satisfying results (for a newbie) even with 2 hour integration.
If I started from scratch and was experienced as you are, I'd go mono. Downside is the clear skies (weather wise) in London are not exactly abundant so you'd have to be even more patient in mono.