A few observations from past experience working in insurance:
1. Companies don't tend to load unless there are particular, negative circumstances, like drink/drug driving, lots of claims etc. You can of course ask the insurers what they intend to do.
2. When companies are quoting,they occasionally allow the NCB/NCD that would have applied if the claim was with them, so it doesn't follow that a new insurer would set the NCB to zero, they may simply give the ncb ur current insurer is applying or invoke their own criteria of protection or step-back. Often this depends on the € amount of claim. You might check with quote engines/brokers using the amount of the claim to see what pops up, or ring around and ask. Criteria may change tho between now and ur renewal date, so no guarantees.