500 Internal Server Error

Hello,

I uploaded a new plugin to my website (www.middlesbroughmeansbusiness.co.uk) and I went to activate it and then suddenly this appears:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, https://www.123-support.co.uk and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Now, I can’t even log-on to the dashboard to delete the plugin!

What do I do?!?!