British butterflies

[D.P.Howson]

This year and last year I have taken a vacation in July/August on the Gower peninsula in South Wales.This year in contrast to last there was a noticable absence of immigrant butterflies,viz no Clouded Yellow(croceus), no Painted Lady(cardui), and few Red Admiral(atalanta). Only Large White(brassicae), which were present in some numbers, might have been immigrants.
Generally, how is the immigrant butterfly scene in UK? Can we look forward to 
much in September?
Turning to the residents,it was nice to see that Small Blue(minimus) seems to be holding its own on Gower, and that Marbled White(galathea) and Silver-washed Fritillary(paphia) are well represented.But my books suggest that there should be colonies of Silver-studded Blue(argus) on the peninsula and these I have never located.Have they died out?
Dave Howson