ALUB, a one year working visa means that you are legally resident in Saudi Arabia and its your place of abode until the completion of your contract. You should be able to apply in Saudi Arabia if you have all the documents you need with you. You can get in touch with the embassy to confirm, but in all honesty you should be fine http://ukinsaudiarabia.fco.gov.uk/en...bassy/contact/
Bear in mind you will need to submit your passport for up to 2 months (although there are ways around this).