The Brexit news are all over the papers and local news. It will be good to keep yourself well informed with the current affairs especially if you are already in the UK on a Tier 1 Visa or even more if you are planning to come to the UK on the Tier 1 Visa. Normally those on the visa and already here in the UK, new regulations do not impact them. New regulations most of the time apply to new applications. Regardless of Brexit or not, it is normally around April of each year that changes are put in place.
The best way to get first hand reliable information and updates on the visa rules would be to visit the official government website https://www.gov.uk/tier-1-entrepreneur. Latest news will be updated there.
Another good way would be to be in touch with an immigration specialist. As the name depicts they will be well informed of the latest updates and will be able to advise you with any issues whether you are already on the visa or planning on a new application.
Unless you are very confident and informed of the immigration laws and application procedures you may be comfortable in applying for it by yourself. However if you are uncertain, seek professional advice. Immigration advisers can help you with most things to do with immigration, including helping you to fill in the right forms and representing you at a tribunal.
Also note that advisers don’t make immigration applications on your behalf and can only give advice. Find a reliable firm that works with immigration solicitors.