Spell-checks have nothing, of course, to do with literacy, or with my, or anyone else's, apparent lack of it. Literacy is a state - "The ability to read and write", my dictionary says - not a means of achieving that state. Is a mathematician any the less numerate because he uses a calculator? Or a painter any the less artistic because he uses an air brush? I think not.
What some of your correspondents have revealed in their innate disdain for things technological is a typically, if not uniquely, English trait. They see computers and spell-checks as undesirable intrusions into an lite world of letters. But perhaps the cause lies not so much within themselves as with their education. We all recognise that there is more honour to be found in scraping a wretched pass in English at Oxbridge than in becoming "Engineering Apprentice of the Year" at Rolls Royce. Or that a Grade C in GCSE Latin is worth much more than a Grade A in metalwork.