As a digital subscriber you have full access to the archive. In my experience this is much the best place to download from.
If you select print you can print as many pages as you wish to pdf.
As has been said above it is a 10 minute job to electronically join the plan pages to get an overall plan. As a hint 1 & 2 and then 3 & 4 etc join edge to edge but 2 & 3 etc have an overlap. There is also an overlap on all vertical joins.
I convert all pages to .jpg (300dpi) using PDF24 and then trim and join to get the full plan in Irfanview. The tiled pages suit my printer very well. If we only got an overall plan converting it to print on an A4 printer to get a model of the right size might be very tricky.