My take on how the eleven species I've seen locally are doing so far:
Peacock - exceptionally good, including a count of 45 in one day
Comma - good, especially early on
Small Tortoiseshell - worryingly few seen compared to last spring (and that was very average)
Red Admiral - no overwinterers seen, but numbers have just started to pick up (immigrants//emergences?)
Speckled Wood - average, but better than the poor spring showing last year
Brimstone - quite poor, with hardly any being seen at the moment
Orange Tip - very good, with daily counts of 20+ regularly currently
Small White - picking up a bit, but nothing exceptional
Green-veined White - slowly increasing, but nothing special
Large White - very few, but this is not unusual in spring on my patch
Holly Blue - reaching the 30-a-day mark, with plenty of new males still emerging. A good year so far, but I can't remember the last poor one here
The unusually sunny and warm weather has no doubt played a part following a winter barely worthy of the name. Only half a dozen air frosts (one of which was at the start of April!) and the average day maximum temperature for each of the three winter months Dec/Jan/Feb was above 10 degrees. I think a few flakes of wet snow might have been spotted in November before my last Holly Blue sighting on 27th.

That was winter. (Heathrow weather observations)
Dave