"...seen as others as scientific rigour. Finland and Iceland don't strike me as countries in hysterics."
The misapplication of the precautionary principle, and refusing to weigh the very quantifiable deaths that occur due to delay of the roll out, is not being rigorous. They know that they are on the hook if side effects are discovered, but they are very much less on the hook for the greater number (and equally directly attributable) deaths due to slower vaccine push.
This is because one is easy for the public to allocate blame for, the other requires a level of subtler thinking.
Literally 15 million doses have been given out in the UK, over months, and any serious side effects (if present) are so rare that they're practically impossible to measure, statistically. This vaccine is safe to within whatever reasonable threshold of safe you want to apply.
This kind of precautionary principle gone mad prizes blame avoidance over saving the most lives, and to seeks to minimise the threat to the regulating body. That's their highest principle, here.
Medicine is, in almost all situations, served well by the precautionary principle. But in a fast-moving pandemic, where doing nothing kills people, refusing to risk the vaccine "as a precaution", in the face of good but imperfect evidence, is a harmful act.