In reply to Tom Ripley Mountain Guide: The problem with the window side of the industry now is that is has become incredibly competetive and the wages are low. You also have to be quite fast to earn a reasonable wage.
Better to look at something like geothechnical stabilisation which involves netting and pinning rock and soil slopes.It is heavy work but quite easy to pick up. Companies like Can,Abcas,Rock Solutions, Vertical Technology .
There are plenty of other employers out there is you have skills with tools doing building maintenance or work in heavy industry like powerstations and refineries.
You will want to look at the ECITB site safety passport(refineries and powerstations) and cscs card for general construction sites.
Another avenue is the wind industry, blade repaire and turbine construction are big areas at the moment.