Well no signs of them yet as my son spent most of the weekend rolling down heather covered hills and didn't pick up any.
Ticks have various stages of lifecycle and are more prone to having lymes disease at diiferent stages. In endemic areas this works out that about one in four ticks will be carrying the virus. They way you get it is by the tick regurgitating some of its stomach contents into your blood stream. This happens when it panics (due to suffocation if you put vasaline etc on it or try to burn it off) or when it stomach is full and it is preparing to detatch (usually over 24hrs later). So Remove them as soon as you can and as gently as possible so that you don't squeeze the stomach area when you are removing it.