Since redundancy in December I have spent a huge amount of time staring at this screen looking at jobs and researching companies.
Aside from the usual corporate stuff on a companies own site I have looked at Glassdoor and Indeed (both seem to use the same reviews!) However the majority of Glassdoor stuff covers reviews sent from (in my case) the states and not the UK.

Apart from these sites how else can I find out about the company? What does anybody else use/do for researching?

Telephone them and ask them what it’s like to work there. You can learn a lot from receptionists. First impressions and all that.