Pretty sure the WTTs stopped being printed some years ago.
I've seen printed freight WTTs available on Ebay from the early 2000s, but I don't recall seeing any for sale that were issued during the last 20 years.
The most recent printed WTT I've got is "Freight and Departmental Train Services" for Section WK (West) 23/05/04 to 11/12/04, issued by Network Rail, Southern Region Waterloo.
By that time it was probably easier to browse the timetable via computer using dedicated planning systems (or TRUST for general users with access to a TOPS terminal). Things like printed weekly "simplifiers" showing trains planned to run could then be generated for use by staff, using regular desktop computers and printers.