Oil ports are definitely part of 50's, forks are the same period and serial number is mid fifties as well.
"Most pre-war Holdsworth's have the frame number on the seatlug. Post WW2 it is generally under the BB, but some 1950's models are stamped on the rear dropout, drive or non-drive side"
http://www.classiclightweights.co.uk/de ... worth.html
Holdsworth frame numbering from the early post-war years is a quite simple sequential mumbering system; frames numbers ran from about 6000 in 1946 through to about 30000 by 1962."
The bike with closest number I've found is 1955 Cyclone Frame No. 18144
on http://www.classiclightweights.co.uk/bu ... worth.html
Only transfer is leading to 70's and an old lady
Her word against Hilary Stone... frame geometry... and serial number..
So still according to me it's 1955 Typhoon.