Tigerbatics,
"I have never heard anyone in British aerobatics use the term 'hammerhead' as an alternative to 'tailslide'. If it was the term used at one time it has long since ceased to be in regular use. Most people hearing the word would assume that a stall turn was meant but the individual had used U.S. terminology."
I was about to suggest that the term was in current use until very recently as I remember discussing the subject with a well-known display pilot whilst flying G-ACDC from Redhill (although we had no thought of going backwards in such a venerable aircraft - Dev Deverill would have killed us even if the a/c didn't!) but I have just realised that this was more than twenty five years ago so it wasn't so recent . . . Time has a strange way of being compressed as one advances in age.
Also, on a wall in the Tiger Club hangar, there was a chart of the Aresti symbols which included what you understand as a Tailslide but then was described as a Hammerhead - positive and negative. BLAC literature of the period made similar references. And I remember much the same thing in the CFI's office but this was in Cyril Nepean Bishop's time, pre-Aresti whose method was adopted some time in the early sixties, if I remember correctly.
With the assistance of the governments of the day, the British light aircraft industry quietly left the field to the American manufacturers and it would be consistent for the domestic terminology to follow a similar path; it seems that it has.
GQ.