"Andy Whitfield" writes:

A solid wooden door is probably stronger than a PVC door but I've
been told wooden doors can't have a 3 point locking system. And
wooden doors are vulnerable around the lock(s) and the wooden frames
also tend to splinter under force.

Ironmongery direct sell a 5 point locking system for wooden doors
(code AB-YWH418). It says in the catalogue that it is for "single and
double rebated doors", but the picture looks like it should fit
perfectly well to a non-rebated door. It needs a separate euro-profile
cylinder and handle and is GBP99 each.

I tried to find it on the website but couldn't, but it is definitely
in the paper catalogue. There seems to be a remnant of it online
http://www.ironmongerydirect.co.uk/Level_3.asp?Code1=WH&Desc1=Window+Hardware&Code2=E &Desc2=Espagnolettes&Colour=ff6600&FONTCOLOUR=FFFF FF
but not the actual product.

ISTR a 3-point system in Screwfix but again cannot find it.

HTH

Peter