I had some UPVC doors installed 4 years ago and they are not really up to scratch. There are noticeable gaps at the tops of the doors and so they are drafty and cold in the winter. I had a 'friend of a friend' install these doors and he has since emigrated to Thailand! Whether or not his dodgy windows influenced his decision I don't know. Anyway, I need to do something about it. Please can you advise on the best way to fill the gap? Do the doors need adjusting with an allen key? If so can I do this myself (my DIY skills are basic)? Or are the doors just faulty in which case, how can I best fill the gaps to block the draft for the winter? Thanks in advance.