How soon to chase up the chain?

So, my situation:

The chain is 3 houses long, I'm the FTB at the bottom end of it.

All the paperwork on my purchase (1) is complete, just waiting for the rest of the chain to be ready to exchange (all searches and surveys done, seller has agreed to take out an indemnity policy for the outstanding issues).

My seller's purchase (2) had their survey scheduled for yesterday (i'm assuming this is done now), and that and the associated mortgage offer are the only outstanding matter (all searches done, associated queries answered, etc)

The onward purchase from their seller (3) is also having their survey done around now (don't have an exact date), but they were also waiting for one of the searches last I heard. That is the top of chain, as the final seller has agreed to move into rented accommodation.

We're currently 11 weeks from when I made my offer. In 6 weeks, my current tenancy ends (end of fixed term, S21 served, and it's a houseshare where the rest of the house is moving out so I can't afford to stay on anyway - the landlord would only agree to a 12 month extension, which was clearly unsuitable). I would obviously like to complete before that happens. I have backup plans if it runs on too long (varying from throwing stuff in storage and taking a week of holiday to staying with friends for a month to throwing my toys out the pram, finding a new tenancy and trying again in 6 months - probably after a pay rise, so with a higher budget).

Is it worth chasing things up again now, or should I wait until next week when there's more likely to be news on the survey/valuations?

Is the 6 week timescale from now realistic? I appreciate that a number of things can go wrong (mortgage offers refused, end of chain deciding not to rent after all), but most of those will be significant enough delays that it's worth me finding another place to rent and looking at the market again.