Yes, you are right to be worried about it. Accidents don't take a holiday at Christmas, in fact it’s their chance for a bit of overtime.
Cutting staff numbers (or changing shift patterns) is a change to the way of working and therefore your employer is obliged by law to carry out a fresh risk assessment which takes into account the changes. The risk assessment should be looking at, amongst other things:
You have a right to ask for a copy of the risk assessment. If you have any concerns after this, or your employer has not (or will not) do a risk assessment, contact your union rep or contact the Health and Safety Executive in confidence (if you are not in a union).