Sorry for taking so long to come back to the thread!
She's fine today, thanks everyone who replied though, it's always good to get other peoples point of view.
She ate her dinner last night as usual and seemed her normal self. On the way upstairs to bed she stopped on the first few stairs and said " mummy ouch" and rubbed her head so she was still aware of it.
I checked on her every hour till about midnight, shining a torch in her eyes to rouse her each time, she didn't seem to amused by this funnily enough! She woke at 2am but this isn't unusual and I just resettled her and she slept till 5 am then came into bed with me till 7 am. All pretty standard night behaviour.
Today she has been her usual self, and I haven't had to watch her as she slept as today she decided napping was not for her and refused to sleep!
She seems to have a small lump on the back of her head, but it doesn't seem to hurt when I pressed on it when I was checking her head.
And it hasn't put her off climbing the stairs, I've been watching her like a hawk all day though.
Thank again, sorry for the essay.