Well, yes and no. I set off, but the Samedan weather was such that I diverted to Altenrhein, sadly.
Great to see you back, tomjnx 
Nearest I ever got to Samedan was at FL129
VFR back then, Zurich would not let us go into their Class C; base FL130.
Timothy wrote:
I need to know by Bad Ragatz whether to turn left for 21 or right or 03. How do I find out which is in use?
Listen to the ATIS. You can very well receive it by then.
Timothy wrote:
How do I know whether LSR11 is active, and what do I do if it is?
NOTAM and DABS
https://www.skybriefing.com/portal/de/dabs
If it is active contact 134.475 for crossing clearance or fly south of the river Inn below 7000 ft which is below the southern part.
Timothy wrote:
On departure I need to go NE. What do I do if either the wind or traffic strongly favours 21?
Take off on 21 and fly the published pattern and leave at the end of the downwind.
Timothy wrote:
What is Zurich Delta?
The ATC unit which handles VFR traffic in Airspace C and D, primarily above FL130 with MIL active or 160 with MIL off.
Delta is a special information frequency for the difficult cases 8-)
Unlike Zürich Information, Delta is staffed (if it is actually staffed) with fully qualified air traffic controllers, that is they can give you clearances, and not just relay them
Thank you all for the great help and advice. I have now flown the routes on X-Plane, with a 9,000’ cloudbase, and I see exactly what I have to do, thank you.
However, some outstanding questions:
Sorry if all this sounds a bit anal, but this does seem to be the kind of destination to benefit from planning and forethought!
Timothy wrote:
Thank you. 03 would actually be more convenient for my route (and not making any valley turns) and (even though it’s rather a way off) all the models say nil wind.
If it is a sunny day with thermals around noon local time the low level wind in the valley will most likely turn to southerly wind due to thermal activity in the high mountains.
When people go there for gliding they usually wait until the wind turns towards a south wind because that means the mountains in the north work. It is not an exact science, just something to keep in mind.
Rwy20 wrote:
I was trying to be helpful
Sorry, that was harsh, I apologise. But I have been flying PA31 for over 30 years, and I do know what Cat it’s in. I often wish it were A 
Thank you. 03 would actually be more convenient for my route (and not making any valley turns) and (even though it’s rather a way off) all the models say nil wind.
I have been many times to LSZS but only in the winter when the low temperatures do help a lot. In a bigger plane I would always do the full straight approach from Maloja or Zernez. Some do a tight circuit, some come from the side valleys etc. but I would land straight.
If the wind is calm, which it usually is in the winter when we come, AFIS is flexible about the runway in use which might help in some cases.
The main thing to realize is there is a significant little hill in the valley between Samedan and St. Moritz. This means on approach to RW03 you have to come in rather high to clear it. The hill is very important when taking off from RW21. You will need serious performance to clear the hill directly. The chart suggests weaker planes do a traffic pattern first to gain altitude. But the valley is quite narrow so I suggest taking off on RW21 if possible which is much easier. Then you have until Zernez to outclimb the mountains. After Zernez the valley becomes much narrower.
Beware of the airport fees for aircraft above 2 tons. Those can be significant and above 4 tons they go crazy. Parking after 2 hours is also quite expensive.
