For my 2015 Vegas 24.1 here are the construction plan numbers:
TTL0103 -- Trunk Layout
TLP0084 -- LP Manifold
TCS0114 -- Chassis, Ford
Depending on the year, your plan numbers might be different. Call Thor Customer Service and ask for those plan names. You will need your VIN to get the correct plans.
Thor Customer Service is (877) 855-2867
Notice your location is England so contacting Thor by email would probably be better for you. Here is the link to Thor Customer Care. Fill out the form and submit it. They will send you the drawing in .pdf format attached to an email reply. https://www.thormotorcoach.com/customer-care/