Thanks - I have also received a reminder to complete my self assessment (as my annual salary used to be above 100k). Should I mention the redundancy payment there as well? I don't think so as I received the payment on 7 May and the self assessment covers the period of 6 April 2013 - 5 April 2014.
The redundancy payment will not need to be disclosed in your 2013/14 tax return. You could make mention in the space for notes that you have left the UK and that you will be submitting a P50 or a P85 for 2014/15 so you will not need a tax return for 2014/15. Whether the tax office will take any notice is open is question but you can but try.