Laura has some great advice on the various teaching roles you can undertake with an agency.
Any of you that have attended one of Protocol Education's social evenings will know that supply teachers tend to be Australian or Canadian and a small minority of us are European. Hence, in most cases, you are here in the UK on a short term basis, possibly on a work visa and are unlikely to still be living and working here in three years time. For most of us this means we have little interest in climbing the career ladder whilst here.
The difference in pay between a supply teacher and teachers in more long term roles is minimal and to be honest supply teachers definitely get paid more proportionately for the amount of work that they do. I have friends (both from the UK and from overseas) who have taken both routes. The ones who work as supply teachers are much happier, have more free time to explore the culture and history of their new home and generally have more positive things to say about the UK's schools and education system. Many teachers, especially those who are newly qualified, who took on long term positions found that they got very little support from the school, often got the classes with the poorest academic achievement or behaviour and were constantly under pressure to do more. The more they struggled the more pressure was put on them and the more stressed they became.
Do you like the routine of knowing where you are going in the morning? Do you like having familiar procedures to follow in school? Do you like working with the same children? If so, then a PPA role is the role for you. PPA stands for planning, preparation and assessment. It involves covering classes within the same school for a period usually no longer than two hours while the class teacher has time outside of the class to plan lessons etc. A PPA teacher would typically cover three different teachers in one school day; one in the morning, one between morning break and lunch and a third after lunch, though this is not set in stone. You may be asked to do some planning but not to the same level as a class teacher would have to.
Having worked as a day to day supply teacher myself before Christmas I have seen the advantages and disadvantages of both. With a PPA role you have the best of both worlds! You are not responsible for any class. If they fail to make progress in maths...not your problem! No staff meetings. No parents meetings. No IEPs. The list goes on. You get to know the children quite well as you teach them weekly (e.g. I teach year 3 every Friday from 9-11am), you are familiar with school routines, you have work colleagues and best of all you have job security (i.e. I know I will be working in my current school until the holidays in July.
Protocol Education also offer a Guaranteed Weekly Agreement to supply teachers from overseas. In brief, it means that you are guaranteed four days work out of five per week and if they can't find work for you (which never happens) you still get paid for four days anyway. There is also the option of taking on a PPA role 2 or 3 days a week and either not working the rest of the time or working as a day to day supply teacher.
A PPA role can be used as a build up to a more permanent role. You get a taste for school life, pick up a lot of useful ideas from various teachers, become familiar with procedures such as marking and doing the register, which may be slightly different to your home country and you quickly start to realise what things you will be looking for/avoiding when finding a more permanent school.
This is the route I have personally chosen. Having worked as both a supply and a PPA teacher I feel that I am more in touch, up to date with and knowledgeable about school life in the UK and I feel that this experience has prepared me for a more permanent position. I'm not telling anyone not to take on a long term role but if you are only starting out teaching in the UK I would recommend starting with supply work and building up to something more long term as there is a lot to adjust to! Personally, I have friends who jumped straight into long term roles on arrival to the UK with very limited knowledge and no experience of the UK's education system. They have since left these long term positions and are now working as supply teachers and without exception every single one of them are much happier now.
Lastly, I met a supply teacher last week who left her long term role in the South of England in February, moved to London and is now earning MORE as a supply teacher! That's more money and less work!