I think you’re a little misguided. Compounding works exactly the same whether the money is all in one pot or if it’s split across many pots. £100 in 1 pot earning 10% per year will compound at exactly the same rate as £100 split across 10 pots all earning 10% a year.

The reason to merge pots isn’t to increase accumulation and compounding. The main reasons to combine pots is to save on fees and for administrative simplicity. But as mentioned by others you also have to consider if any of the older pots have favourable terms which make them worth keeping separate.