Grahame
If an individual is not registered they would be unable to work unsupervised. I am currently on the clinical scientist grade but am in the process of an application to HPC. I can currently work undersupervision of my line manager, if I don't manage to get state registration by the time the HPC close the transitional arrangements in July I simply call myself something else as it would be illegal to claim to be a clinical scientist. I have discussed this with my line manager and he said I could call myself an equipment manager as this is not a protected title and work under his supervison (using the term loosely).
Yes state registration is important but by not having it won't automatically put you out of the job. It just means you will have to work under supervision (well on paper at least) and call yourself something other than Clinical Technologist as that will be a protected title. I suspect EBME technologist would be acceptable as this is not a protected title.