TUPE transfer — our practice is merging with another next April, what do I need to do?

We've been told two practices are merging in April under a PCN model. I'm PM of the smaller one (8 staff). I understand TUPE applies but I've never been through a merger before. What are the key steps and timelines? Particularly worried about harmonising different T&Cs — the other practice has better holiday allowances than us. Would really appreciate a rough timeline of what I should be doing now vs in the run-up.