Hi peter, probably a bit late but I enlarged the photo of your velocette and think it may actually be a scrambler and possibly a bit earlier than 1963. at least the frame and fittings indicate that.
First from the photo it appears to have the oil tank fitted to the left side of the bike and an early air filter on the right.Some of the early scramblers were like this.
Secondly the shocks.are the early type 1955 to 1959.
It also appears to have a remote float carb which may be an AMAL
TT, although difficult to tell from the photo.
Take a look at ehere the swing arms are clamped to the frame pivot. If there are a couple of screws threaded from the individual swings arms through to the swing arm axle then it probably is a scrambler frame.