Trademark infringement?

First, tradenames (company names) are not the same as trademarks and are trademarks only if used as such.  Second, rights in the US are based on use, not registration, so if you registered your company name prior to the filing date of the Madrid trademark application, you have superior rights to the name ABC and can oppose registration of the ABC trademark by the British company in the US. Furthermore, if the difference between the industry you are in and that the British company is such that a purchasor of the goods of your company would not be confused into thinking it is sponsored or made by the British company, or vice verse, there may be no likelihood that the British company could successful block use by you of your company name. I have greatly simplified the situation and you need to consult with a trademark attorney who can review the specific facts and advise you more accurately than is possible via this website.