This year I am trying container tomatoes for the very first time. I
have been recommended three varieties but was wondering when to start
the seeds...

Variety 1 : Paul Robeson (will have a cage) indeterminate 75 days
Variety 2 : Patio Orange determinate 52 days
Variety 3 : Gold Nugget determinate 55 days

They will be seeded in unheated propagator trays with 3" pots indoors
They will be transplanted to 5" pots to increase in size indoors
They will be gradually hardened off on fine days where possible
They will be transplanted to 14" terracotta pots on a sheltered west
facing wall

I am in Edinburgh, a coastal town on the east side of southern
Scotland. We are still having frosts. My questions are...

1. When should I start my seeds?
2. When should I aim to have them outdoors?
3. Do I need to start a second crop of the Patio Orange/Gold Nugget to
last me the season - will each crop all in one rush or staggered
throughout the season?

Thanks for the help folks.