On 29/08/2016 23:29, David Lang wrote:

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This email has been checked for viruses by Avast antivirus software.
https://www.avast.con/antivirus is SPAMWARE

Was that me that's been hijacked by bloody Avast?
That's it, AVAST has now been removed and replaced by Avira!

Decorators caulk?

Unfortunately the problem lies in that the back box isn't flush with the
surface of the plasterboard so there's nothing to give it (or any other
filler) structural stability, i.e. you're trying to fill a 1 sided hole
which is doomed to failure.