Visual tools have disappeared

Hi,

I’ve just recently moved hosting from GoDaddy to Heart Internet (in the UK).
AS much as I’ve become very despondent with customer service in general from Tech companies, probably due to the variety out there.

However, due to my old theme ‘Structure’ not working properly with my new host, & I was pretty much left to debug lines of code on my own. I thought I’d get rid of the problem all together & install a new theme.

I installed & modified the ‘Customizr’ theme. All seemed well, a draft post published well & I thought that was the end of my woes.

Sadly not, When I have come to write a post today, the visual tools have disappeared & the text colour is white, on a white background.

I have checked the usual suspects:
-The visual editor box in my profile
-Uploaded a new wp-admin folder to my server (that didn’t go well & reverted back)
-Tried another theme – TwentyEleven, & the problem still persists
-Troubleshoot my plugins, activate etc
-Clear cache repeatedly after each operation to solve problem.

I’m not an IT expert, in fact I’m a chef by trade, so please, any suggestions keep them like you’re speaking to a simpleton.

Many thx in advance