I currently use Microsoft Security Essentials to protect my computer but BT have now offered me free of charge:

Free NetProtect Plus - Advanced McAfee security software helps protect your computer from online hackers, viruses, and ID theft. Plus free Family Protection, which has parental controls, search blockers and time limits, to ensure children don't see anything they shouldn't. To protect up to seven PCs,

Should I switch?

Many thanks for your kind advice.