UKH

my left knee has developed a pain ive not had before (anterior), from looking online it seems to fit with patella tracking issue. Im confident its not an ACL tear. Im currently resting it as most exercise seems to aggrevate it except cycling on the flat.

Ive self massaged and rolled my thigh muscles and glutes - the only tender area is the vastus medialis. Im guessing that Im overusing this muscle and that I need to strengthen the lateralis and gluteals to balance it? Just thought Id check im on the right track, thanks.

I think from memory knee extension exercises are good for that. I had similar issues a few years ago and they cleared it up a treat. 
In general, doing weights (squats etc) is good for my knees, which can play up a bit from cycling. 

“Simple patella problem” 

just wish there was a “simple patella solution”

had mine since last April...

We need better location details for our unsound and dangerous guesses!

the VMO is keen on atrophy in many knee injuries so could be secondary that that muscle is tired.  I would roll the top of your quads and hamstrings well and do lots of hip flexor stretching and see if that helps as well as looking at VMO, gluteal and tfl strengthening  

Our local running stores physio is doing online work, that might be better for your knee  in the long run. 

thanks - from compaing my thighs, the left VMO muscle is bigger than the right, and also the left lateralis is smaller than the right, so makes me think the vmo is dominant on the left leg. The asymptomatic right leg the muscles look more equal in size.

Who is your local physio?

https://www.physio-form.co.uk in Burton. The front of the shop is a running shop, the back is a physio and both sides have served us well since moving down here.

I think it's just quad weakness in general, I can cycle on road no problem but when walking about a mile is uncomfortable, no running for quite a while id imagine now. Doing home exercises and stretches.