well here it is…
i went out for a pootle this morning on my road bike around terrington, but as i got the bike up to 44mph the front end started to shake from side to side as though the forks were made of jelly !! ( there not ive checked, and are some sort of metal !!)
so anyone know why this would happen ?

Sure its not the front hub/QR? – Have you wiggled the wheel/RIm?

Headset might be slightly loose or worn allowing the oscillation to start at certain speeds. Dragging the front brake can sometimes set it off as it rakes the forks back slighty under the bike. Can be very very scarey, had it on the Fred Whitton on knocking on 50mph on Kirkstone 😯 though I was going make a contact fit with a drystone wall!

Speed wobble, shimmy, or tankslapper in motorbike speak
http://www.singletrackworld.com/forum/topic/speed-wobble-1

thanks chaps…
on inspection it looks like the headset cups are a little too large and have been bodged with black pape to make them fit the frame!!
time for a new headset i think