Hosted webspace lost USER and DATABASE visibility and access

[#1]

I have historical webspace which hosts my website.  Today I can still login and access the control panel and see all my files in FILEMANAGER.   ...   But my MYSQL username has disappeared and no databases are found, despite the fact that I can see it in filemanger.

By setting a new user MYSQLmanager I can create a new database OK so planned a workaround to restore my data backup to the new db.  However, when I go in to MYPHP to setup and restore the new database MYPHPADMIN is unresponsive on any of the tabs.

This problem does not occur on other hosted webspace so the problem appears server based.  

Update -  -I now find it has lost the USER I set up an hour ago and my website has ceased functioning at all.  Can anybody suggest where I go from here, I am baffled and the guys on the helpdesk at PlusNet have no experience of this type of problem.

Further update - my website has come back up but my new user and db remains missing?????  15.40 hrs 4th Jan21

[#2]

This gets worse - My website is now inaccessible by me and I can see it is under some form of ddos attack.  I want to disable the site while I fix it but I cannot  open the webpage hosting.plus.net to login and shut my site down. 

Does Bob Pullen still work for Plusnet, I need his expertise as the other PN staff are not trained in this area at all.

Any suggestions, beyond moving the whole website to another provider?