The London UK market is currently fantastic for developers with extensive Java development experience. There are lots of jobs and therefore lots of opportunity to find a really good position with a good salary. Of course you will need a visa, and I wouldn’t recommend anyone come to the UK without the right to work in this country, but if you do have that visa, then there hasn’t been a better time all year than now.
Coming to work in the UK can be an exciting, challenging and rewarding career choice that will give you an international experience that can’t get anywhere else in the world, and will shape your career for the rest of your life; however if you aren’t properly prepared you will struggle to get what you want.
What you will need:

The right to work in the UK
It is still next to impossible to be sponsored by a company in the UK, as such if you do not have the right to work here, it is advisable to not relocate to the UK.
The technical skills
Check on the English job websites that you have the right technical skills for a role in the UK. Some countries tend to still be using the old “EJBs and app server” model which is generally (although not totally) defunct in the UK today. Unless you have extensive low level core Java (think writing your own threads, TCP/IP sockets etc) you will also need at least basic Spring. If you don’t have it, getting an online certification will be very useful. In general you should brush up on all your technical skills and make sure there is nothing on your CV that you would not be prepared to be grilled on in that first interview. One good tip is starting your own blog and posting some of your best bits of code / ideas on there, this can be very helpful to candidates without an established track record in the UK
The English
The London IT market, especially in finance, is probably the most international job market in the world – it is not simply that you will often find yourself in a team where everybody comes from different countries, but its not uncommon to find teams without a single British developer in the team. So communication skills are EXTREMELY important. Basically if you can’t understand spoken English and speak it easily and fluently, you will not find a programming job easily and if you do, it won’t be very good. A good rule of thumb is whether you can answer a set of technical Java questions reasonably easily. If the standard of your spoken English is poor, you should either take a course before you leave or one better – if you can afford it – relocate to the UK and don’t start your search until you have improved it.
A Curriculum Vitae
(The word Resume is American, and is best left on that side of the Atlantic) Globally there are roughly 2 types of CV, the Curriculum Vitae that many of us know and love and the “Europass” CV – hated by all in London. Hated of course because it is completely useless as a professional document in this country. As a recruiter I need to know what companies you have worked for, what dates you were there for, what you were doing for each company and which technologies you used. Instead the Europass is a hideous piece of bureau-bum designed EU-construct aren’t-we-so-different cr@p which is genuinely completely useless and many a good developer has been over-looked simply because their experience was delivered in the utterly indecipherable format of the dreaded Europass. If you have one AVOID, REWRITE or FORGET it
FLEXIBILITY TO RELOCATE
Most hiring managers can get through the first and often the second stage interview in their process on the telephone or through Skype. However no-one is going to employ someone they haven’t met and therefore an appetite for coming over to the UK for interviews and being flexible about it will be very helpful. Today it is rare occurrence that a British company will pay for a candidate to fly over to the UK for an interview. Any good recruiter should help to arrange the process to make it as easy and cost effective for you as possible but you have to realise you are competing with developers who are already in the UK – afterall what is the point of companies paying to see you when they don’t have to pay anyone who is already in the UK. You will also need to have made up your mind that you really do want to relocate to the UK and be prepared to move over as soon as possible once you secure that dream job. Talking it through with wives / girlfriends / Cuban-US-visa-seeking-lovers before hand will be a very good idea.
FINALLY: TENACITY AND PATIENCE
It is a good market in the UK for good Java developers and its rare that I hear of foreign candidates who have the right to work in the UK, the marketable technical skills, good English communication skills, a proper Curriculum Vitae and flexibility to attend interviews going home having failed to find a job. However, nothing good comes easy in this world, and no matter how active the market is you will always take a couple of weeks or maybe even months to find the right position for you. So be brave, be tenacious about your applications and have patience that the right role will come along.