In reply to mark s:
According to this link, no exemption (unless you tried it under the 3rd from last reason below):
http://en.wikipedia.org/wiki/Juries_in_England_and_Wales#Eligibility_for_ju...
People are excused from jury service if:
-they are currently a resident in a hospital or other similar institution, due to attend a hospital appointment or operation or recovering from an operation;
-they regularly visit a medical practitioner for treatment;
-they are in guardianship under section 7 of the Mental Health Act 1983;
-a judge has decided they are not capable of managing and administering property or affairs because of mental disorder/mental health problem
-other medical reasons preclude their service. Medical certificates are only required if the Jury Central Summoning Bureau asks for one;
-they have already booked and paid for an important family event such as a wedding or a holiday;
-they have urgent work commitments which, if not completed on time, would have a detrimental effect to their business;
-they have been on jury service in the past two years (except coroner's juries), or the individual has been exempted from jury service for a period of time that has not yet ended.
-they are a full-time member of Her Majesty's naval, military or air forces and their commanding officer certifies that their absence would prejudice the efficiency of the service.
I received a citation a couple of months ago (for Scottish jury service) and it was pretty much the same IIRC. I was excused as I'd served within the previous 2 years.