Hi Buggy,
Ifield (also known as the Rusper Road site) is my local Brown Hairstreak hot-spot, but they are seen here in low numbers only. There has been a lot of Blackthorn removed recently, so this may affect numbers for this season. However the habitat remains good and there should be some re-generation of growth in future years. In the circumstances I cannot guarantee that you will see this species here, but it is easy to walk to from Ifield Railway station. Let me know if you need directions. There is another site (known as Willoughby Fields TQ257 387) just to the north-east where Dave Browne (Buchan Boy) saw a couple last year, but I have not been there. The Horley/Gatwick site was visited by Neil Hulme a few years back with some success, but I am not familiar with the location.
Hope this helps
Vince