Anyone have any input?

I always think of Bougainvillea as a full sun plant and I can't believe it would be happy indoors, and I am not sure that even grow lights would be enough. I also wonder about your soil which looks fairly fine-textured. In general container plants do best in free-draining soil that has components which won't break down quickly like pummice. There is a container forum where this question might get more attention.

Bougainvillea like to dry out a little between waterings. When you water, let it get a little bit dry until about an inch down before you rewater. If they arent growing a whole lot or flowering they dont need as much water. You could try mixing some perlite into the soil to promote drainage. Make sure they don't have heat blowing directly on them from a heat vent etc. Give them as much light as possible.

Sean, I believe you have a conservatory. That would be the place for it.

It's been in the conservatory too with the same issue with this one. Can't seem to find out what's wrong with it. I did research it and found out it likes to dry out so I do water it a lot less than others. I think it does dry out enough. I've tried a few things over last few months. Only thing I can think of is the soil. I'm not sure what Media I can buy in uk that would be Good for it

John Innes no.3. And a bigger pot.

I have that soil however it doesn't seem to drain much. What do people usually mix with to increase drainage? I've tried perlite but unless I use a massive % of perlite I don't see any difference