Where to get Cortisone injections in London/Essex?

Hi,

I'm suffering from tenosynovitis (according to an MRI scan) in the tendons of my left knee which has left me virtually housebound.

I've heard that cortisone injections can be very effective. Please can anyone recommend where I can get this done at short notice in London or Essex?

It's been bothering me for 5 months and I need to get it sorted asap!

The injury was originally caused by cycling, which I initially recovered from, but was significantly aggravated by physiotherapy. I've seen osteopaths too which has been helpful, but slow progress. (Treatment where I live - Israel - has been poor.)

Thanks!