In the end I planted it in some biobizz all mix to see how seedling would react (it burnt, lesson learnt I use potting soil for germination now).
Well I carried on watering this seedling and then potted up with more biobizz to a 16 litre fabric pot. I kept it in the conservatory where it's light but doesn't get direct light but on my days off I'd stick it outside in the sun. All she's had is water every few days and 2 top dressings of a scoop of Plagron bat guano after her pistils showed.
Just sharing out of curiosity. Like I said, she was only planted to see how it'd react to the soil. This is all still new to me. I have thought about chucking it a few times (especially when people come over and try going in the conservatory) but didn't have the heart so kept her for the summer. Looks like I might get some smoke from her now.
Anyway, here's BAGSY grown by water, soil, sun and bat shit. Planted may day bank holiday weekend. She's just over 7 foot.