Yes gardenmad, you should be concerned, but you had the common sense to realise that all was not right. Ideally you should now change your password to access your email.
I'm the local Neighbourhood Watch rep for two local streets and also receive warnings from our coordinator about these upsetting emails.
If you are worried about any email of this nature, just go to <
http://www.actionfraud.police.uk/scam-emails > and follow their advice.
You say your computer was blocked, but 'returned'. How did that work? I hope you didn't part with any money. There are freeware anti virus programmes out there like AVG [just Google it] and others. I use McAfee, which costs about £40.00/annum. It is updated automatically on a regular basis and provides its own firewall. Norton is also very good. Windows also has a built-in firewall turned on by default, but you can check by clicking the Start button, then Control Panel, then Security. You should find the firewall on, but it's easy from there to turn it on. This is on XP but later editions of Windows are not that different. If you're not sure, just Google "How do I turn on the Windows firewall" and pick the operating system you have.
None of them should be considered absolutely secure but unless you're a high-powered surfer going into every esoteric search engine and website, then you should be fine. Make sure your email password is not easy to guess. A good way is to choose the first [or even last] letter of the words of a poem or song you like, add or insert a capital letter or number and you should be fine. Let us know how you get on. Don't be frightened, just be cautious, which you apparently are already.