I figured it out in the end. I had tried a union query but it wasn't working and then I read that I need to use an alias if I...

It is all good now. It turns out putting the indexes on the table worked miracles. It now takes 1 minute and 16 seconds. Brilliant!!!

Thanks for you help guys. I...

1. It does exist yes. I have already created it and populated with the keyword data.

2. No indexes yet. Will add them in.

3. It does work with a particular set...

I did try that. For some reason it just sits running for ages and ages and nothing happens. No rows get updated. I don't know why.