Wadkin went bust a few years ago there is a new company in the UK that has the old drawings etc and can make parts to order but not whole machines
I run a XE220 machine must be about twenty years old now it goes well no plans to change it
The XE series was made on a GS series chassis ( the small slow planer) with high speed jointed spindles outriger bearings etc off the XJ series so it could run at higher feed speed (100 feet per minute)
so it is a sort of compromise between the fast to set up slow to run GS and the more complicated to set up but faster to run XJ
I don't think there was a XE446 generally the numbers refer to how wide timber it can take ie my XE220 can take a 220 millimeter wide board