Seventh time lucky, put loads of silicone on the transparent washer and
left it for 40 minutes.

Now next question. The chrome tube which screws into the waste and then
fits into the top of the trap seems lose. I can tighten it up but the
trap still slides up and down on this pipe, am I missing a part here? I
thought by tightening it this would secure it but it looks to me as it
will gradually fall off.

Thanks for your reply!

Cheers

Richard