Hi, some advice would be appreciated!

We've had an extension built and wish to fit a venetian blind (already made
to measure and delivered) into the window recess.

Unfortunately there is a steel lintel right above the plasterboard which
prevents me top mounting the blind in the way I've done before, using
plasterboard plugs. As the windows are upvc I'm really not sure about making
holes in the window frame, how to do it or whether it would work. The
builder has advised that the window company won't invalidate the guarantee
if I do this.

This must be a reasonably common problem - can someone advise? Is there
another solution using some kind of adhesive? ("No more nails?") And if the
answer is to make holes in the plastic window frame, any advice on how to do
it so it won't fall down?

Thanks.

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