Definitely a TT frame, and a nice one at that. As you say, Stan Pike died in November 1983 but it could be a "Stan Pike" frame marketed through Competition Cycles of NW London or Argos of Bristol rather than from Stan's Crewkerne workshop. Bill Philbrook of Gillingham in Kent was building special TT frames with many similar features back in 1973 or 1974, so no real reason I can see to think the frame post-dates Stan's death, he was still building frames in February 1983. You might find this a useful source of additional info:

http://www.timetriallingforum.co.uk/...howtopic=20484

No idea about the forks you mention, can you show photos?