Major effects of tick bites:

- Lyme disease (watch for a spreading circular rash that develops over a few days or weeks)

- Eastern European encephalitis (not found in the UK yet as far as I know)

Lyme disease is a rapidly worsening problem, but can be treated by antibiotics if you get it dealt with early. Ignore it for months and you've got it for life. Eastern European encephalitis won't usually cause serious damage but it's untreatable. It can be immunized against.