Hello,
I would say it's a good idea to come and see the place you are going to live and work if at all possible :) What do you do if you don't mind me asking, and what attracts you about living in England as obviously it's a big place with lots of diversity, big cities, small towns, rural areas etc?
The least risky/most hassle-free way is probably to try and get a job in Northern Ireland/your current hometown, with an employer who also has offices or premises somewhere in England, and then apply for a transfer. If you want to live in a particular part of England you might be waiting a long time though?
Otherwise you'll need to start applying for jobs in England and come over for interviews. Employers these days are often prepared to do at least first interviews via Skype, and many will pay travel expenses to get you to the interview, if it's a professional or managerial level role.
Or a more risky option but possible if you are looking at minimum wage type jobs in a city is to simply build up enough money to pay for rent in a house share or cheap AirBnB in your chosen location for 3-6 months (you can work out how much this will be online) + living expenses, then take the plunge and come over here and start applying for jobs like mad - it's what many young Londoners do. If you have done your research properly you may get work much quicker than the 3 months as there are usually lots of jobs in bars, cafes, supermarkets etc going (plus there are always benefits if you really can't get work....)