The real question is going to be when you are looking to teach. If you are looking to step in immediately then you will have to show that you have suitable teaching qualifications and levels of education. To figure this out you should contact the UKNARIC. They will look at your degree and teaching certification to see if you pass muster for a temporary teaching qualification which will then give you a set amount of time to work towards the english qualifications. Alternatively, you could start looking into some of the teaching agencies (Capita, Beacon, Recruit, etc.) over there to see what they think you will need, they may also be an easier in-route to your first few jobs.