So yes I think it’s the 32A which I’d use but probably drop the current setting in the vehicle as I don’t want to trip their fuses. Anyway to suss out what the circuit can take so I get max benefit and minimum in law hassle?
Not in general, which is why when putting in something specifically for charging, proper chargepoints are a good thing and 32A commandos are not.
However, if you do find a 32A socket it is convenient to be able to use it. 32A commando sockets are pretty rare on domestic premises, and in general you would expect it to be on a circuit to support at least 20A (as otherwise the smaller and much more common 16A socket would have been used). If you know why it was originally installed, or can find the breaker that feeds it, then that may give an indication.
If it isn't on a dedicated circuit with its own breaker, then treat it with great suspicion.
If this is a normal domestic single-phase supply, then there may be an issue not with overloading the circuit, but the supply to the entire house - which could cause great trouble and inconvenience if you end up blowing the supplier's fuse. Again, hard to tell in the general case where you don't know what the rating of the supply is, nor what the load of the rest of the house is likely to be. Best to avoid charging at times of peak usage (electric showers? Hot tub? electric heating?). Typically not an issue charging overnight, so if you trust the charging setup you can just turn it on last thing at night when nobody else is using power; but on the other hand, for a charging setup you haven't used previously, it's always good advice to start it charging at least an hour before going to bed so that you can give it a check-over that nothing is getting hot or otherwise giving trouble.
2) separately, TfL are putting in many chargers across London that have the charge point/ bay in the wrong place for a Tesla. Is it possible/legal to use a Type 2 extension lead to make this work?
Type2 extension leads are not legal and not widely available. However, you would only want one if you had a chargepoint with the cable attached - most standard chargepoints have a socket, so you need to provide a type2 to type2 cable of sufficient length. A cable 7m long covers pretty much any situation; so long as you are prepared to park the car facing the direction to give the shortest reach, normally a shorter one would be fine.
I'm not sure what you are referring to with respect to TfL: the historical stuff (ex-TFL, now Source London) is socketed; Source London's new points have a tethered type1 cable at low power (that you can't use and wouldn't want to), but also a socket. If you mean rapid chargepoints that happen to have an AC output (on a type2 tethered cable), then you shouldn't be using that in the first place as it's too slow; you should be using the Tesla CHAdeMO adapter to access the CHAdeMO output on the same units.
