The English, punctuation and grammar are deplorable.
You may therefore rest assured that you are dealing with someone who has been educated here within the last ten years, and not with someone working out of an Internet cafe in Lagos, who'd have tried much harder.
Do claim your TWO HUNDRED AND FIFTY THOUSAND BRITISH POUNDS although you have invalidated yourself by not keeping your winning informationconfidential.
These threads come up about once a week, much like "How do I get a Free Upgrad3?" on SLF. If you are seriously asking whether this is a scam, I hope that you invest some time soon in learning about the more credible scams doing the rounds.
BOFH