Dodo,
I don't like to contradict people who give their opinions freely on this website, but the minimum notice legislation applies to both employees and employers and states that anybody with service between 13 weeks and two years have to give 1 weeks notice, service between 2 yrs and 5 yrs have to give two weeks notice, service between 5yrs and 10yrs give four weeks notice, service between 10 and 15 yrs give six weeks notice and service greater than 15 years give eight weeks notice.
Just rereading your email you've worked 3.5 years, therefore you are obliged to give 2 weeks notice.
Also if you are working for a decent employer and wish to leave on good terms it's always a good idea to give a reasonable amount of notice. There's always a chance that your new job isn't quite what you expect it to be.
Best of luck with the new job
Past30