Ooh blimey Martin...at least twenty five years ago, if not more. As far as I know, mine was the first Spearfish to be bought in Sussex, or so the guy in the model shop (now long gone...
) told me.
I had the Spearfish and my cousin down in Chichester had a Fantome, with the Fox 22cc spark ignition motor in it. With the OPS .65 motor, the Spearfish was a lot quicker than his Fantome...much to his annoyance.
The Bullet 30 motor was an ideal motor for the Spearfish, it was as quick, if not quicker, than the ic motor until the batteries started to die away, but she would go a good 12-15 minutes on a charge. No speed controllers back then, just microswitches...all or nothing!