Well firstly I would suggest that you look into getting an LPA for his finances so that when the time comes you can access these pensions for him.
It may be worth speaking with a financial advisor about this e.g. if you cash in the pensions now , what would that do to the longer term amounts , can you afford not to cash them in, are their any lump sums that you need to consider etc. some companies will give you a 30minute free of charge consultation. Pension wise is limited to certain types of pensions. Each pension will probably have their own way of dealing with this so you both may need to make contact with them about how to proceed. Don’t forget that your husband should be able to get his state pension when he is 67 , it might be worth looking to see if his NI contributions meet the criteria for a full state pension.
As your husband is currently still working I’m guessing that he is at the early stages of his diagnosis and so hopefully he can have a say in managing this and dealing with the pension companies concerned.