Legally, an employer can-not give a bad refrance as it is regarded a slander.. It's what they dont say about you or refuse to give you a refrance..
Be carefull, when taking time out, after 9/11, the govemnet clamped down on airside secuity, including issue of passes(
www.disclosurescotland.co.uk/airside.htm) they will want to know what you have been doing for a period of time and if you take time out, how are you going to quantify this?