Hello, for the best uPVC door and window security i suggest ->
1.install multi purpose bolts ad removed to the top and bottom corner of the door or window. Very easy and quick to install. Just make sure you have got good self tapping screws to secure the bolt strongly on the door.
You can buy such a bolts in any DIY store and cost around £15.
Definitely one of the best security for uPVC door if installed correctly!
2.Good Quality British Standard or High security cylinder. For most uPVC doors its euro cylinder type. You must make sure the cylinder has British standard kite mark and BS numbering. That means that the cylinder its insurance approved and its in most cases Anti Snap,Anti drill, Anti Pick, Anti Bump.
Anti drill doesn't mean its not possible to drill, but the drilling time takes much much longer then standard cylinders makes it for thieve very difficult to brake it.
3.For securing front door incase you have letter box make sure you install letter box restrictor or letter box cage and never leave your keys near by the door.
4. Simple intruders alarm or alarm system connected to the local police.
Hope this help!