UKH

How quickly do the crags at holyhead mountain and the other gogarth crags dry after rain? 

Holyhead is clean and rough, it is climbable wet or dry at almost the same standard. As it is clean it will quickly in the right conditions, or not at all in cool humid clag.

jk

When I climbed there in August last year it lashed it down for most of the day (including bouncing rain while sat in the cafe), we left the cafe about 15 minutes after the rain ended and by the time we reached the bottom of the crag it was more or less dry.

That's what i was hoping the answer would be haha

Temperature is a big factor as well though, if the rock isn't holding a lot of energy then like anywhere, drying time can be variable.

In hot conditions anywhere can literally rain all day, and then evaporate almost immediately, but given it is a bit colder across the UK than normal, the drying time at my local crag is slower.