Woodland species

[eccles]

I live near Willsbridge valley, an 8 hectare local wildlife trust comprising mainly of mixed deciduous woodland astride a brook. There are a few open areas with bramble and a small meadow. Last year for the first time at the site I saw a single, and rather tatty male silver washed fritillary and assumed it was a vagrant. Then two days ago I saw another, followed yesterday by a single white admiral. The SWF was there again today, at least I think it was the same one.
I assume again that these are vagrants, although where from I have no idea, but this leads me to ask the question: what sort of size of woodland is necessary to support colonies of these two species? Is 8 hectare big enough?
For the SWF, I saw common dog violet flowering earlier this year in several places and there are several oaks of different ages. For the WA, I only know of one place on the site where there is honeysuckle but it's quite a large plant.
Currently there are speckled wood, gatekeeper, meadow brown, ringlet, holly blue, red admiral, comma, peacock, brimstone, orange tip, large, small and green veined whites regularly breeding there.
Any comments appreciated.