http://www.companypartners.com/content/resource/trademarks
I think you’re safe unless you have the same/similar logo and his is registered and yours isn’t. They need to be a big firm to afford the legal costs! There are lots of Fishermania, Fishamania, Fishomania fish and chip shops, even tackle shops but if any of them called themselves “Fish’O’Mania” they’d be in trouble because the name constructed in that manner ie with the ‘O’ in the middle would be violating the trademark.
If the name you have is spelt unusually (like the ‘Kover’ in Korda Kover insurance for example) and it clashes with their name for similar service/goods, then it could be an issue but I think it would depend on who got there first – not registering the name but actually using it. After all, they could have copied your name, registered it and try to put you out of business. That’s not right.