Mary, I think it's dangerous comparing spinning in your average glider (with long, slender wings and very sedate spin behaviour as a result) to spinning in your average spamcan (with short, stubby wings and very aggressive and sometimes unpredictable spin behaviour).
According to your post, the BGA considers 700' the minimum for spinning a glider and you claim that spin recovery takes up 300'. That in itself shows that spinning a glider is a very leisurely affair. For comparison, I regularly spin an R2160, which is an aerobatics-capable Robin. A one turn spin and subsequent recovery results in a minimum of 1000' height loss, with each additional turn taking up about 350'. Each turn takes approximately a single second although I have to admit that I'm not concerned with timekeeping while spinning. But yes, that is approximately 360 degrees and 350' height loss per second, give or take. We don't initiate spins at less than 3500' - five times what the BGA considers a safe height.
I agree with Bose-X and others who think that spinning was rightfully removed from the PPL syllabus. You don't spin in straight and level flight, and the only time when you would have a chance of a spin is when mishandling the turn to final, where you have insufficient height to recover in any case. Stall/spin awareness is much, much more important. But I also do like Skylarks instructor, who demonstrates (not teaches) 10 minutes of aerobatics somewhere during the course.
At my club we have a special "Unusual Attitudes" day, twice a year, where PPL students and post-PPL pilots go up with an experienced instructor/coach, in an aerobatics plane, to demonstrate and experience spins, accellerated and full power stalls and a few other edge-of-the envelope things, plus some basic aerobatics manoevers. It was this day that got me hooked on aerobatics. But more importantly, it gave me a new appreciation for the dangers of the turn-to-final with too little speed.