The Spean Bridge colony is spread out and thin on the ground, and the colony is tiny. 2 years ago I found 2 adults only, and in one area.
Assuming that you will be using public transport, then the options might be limited. I've looked at train stations near to sites I'd recommend and most are at least 8km away. I haven't checked on buses.
For NBA ssp. artaxerxes, I suggest you ask Iain Cowe (IAC), the regional expert in the Borders. I don't know about the current status at Arthur's Seat.
For Chequered Skipper, I'd recommend Glasdrum Wood which is very reliable, and at the southern edge of its range. While the species is found at other sites, I've never seen it in any numbers except at Glasdrum. Ariundle is good, but it is a large site and lots of walking required. And it's out of the way somewhat.
For Large Heath and Mountain Ringlet, you need to decide which subspecies you're going to go for, especially since they emerge at different times between north and south.
For Mountain Ringlet, I'd recommend Ben Lawers (Scotland) or Irton Fell (Cumbria, and an early site).
For Large Heath I'd recommend Glen Loy (ssp. scotica), where you can also find Chequered Skipper, and Meathop Moss (ssp. davus). Whixall Moss is supposed to be pretty good too.
[Edit] Looks like Dave and I agree
Cheers,
- Pete