This stuff I've been using called Mikrobs has been keeping my plants good and green. You just mix in water every 7-10 days. I'm in the process of flowering out some plants and getting a little more info on how it helps flowering and overall growth. I feel its worth a try, especially since my veg stuff is nice and green. The clones have loved it once I gave them a light dose there growing great!!!!
I'm in the USA, I'm not sure I guess Amazon would ship to UK?? I'm not sure on that, Mikrobs is worth trying, I'm doing more testing with it and will have flowering info. They recommended 4-6 weeks adding Mikrobs in flowering depending on strain. So I'm trying it, and love the Veg stage, but I'm getting ready to flower a bunch I've gave Mikrobs