. . . and just how long is it since either of these versions was used in a Christian church service in England? Or anywhere?
Probably several times a week in most churches, Matt - depending on how many services that church holds on a Sunday and whether they also hold mid-week services - like a mid-week communion service or have Bible Study groups where it may be said as part of the prayer time. On our projection software at church, we have 4 different versions of the prayer for use with different congregations.
How many people saying the prayer in church or in private understand that 'temptation' in the Lord's prayer does not mean what they think it means?
The Lord's Prayer is quite a common sermon topic, and each preacher may or may not choose to concentrate on this particular 'do not ... but' pairing. It should also be remembered that Bibliclally, temptation is not regarded as a sin; the sin is giving into it. After all, Jesus was tempted whilst in the desert.
Other than biblical scholars, of course?
The advantage of having the Bible in English, and other native languages is that one doesn't have to be a Bible scholar to understand things. Many of us have access to commentaries - both in hard-copy and online - neither of which require Biblical scholar status to be able to read and understand.
And why has this only come to light now, when the reason for the request needing to be made by the supplicant is being questioned?
Has it? As far as I'm aware, it has been discussed and sermonised on for at least as long as I've been alive. As for your earier comment about never hearing Greek or Latin referred to by a preacher, your experience is pretty well diametrically the opposite of mine - I can only think of one clergyman whose preaching I've known over a decent period of time (ie not just a one-off sermon) who never referred to Greek and/or Latin in their sermons. I haven't preached for some time now, but when I did, both here in the UK and in nepal, I too would refer to the original language of a passage to try to draw out its original meaning, so that one can apply it honestly toi modern-day situations.
Why are the versions that you quote above not used today? Well, not to my knowledge anyway!
There are a number of versions that reflect the same meaning as the examples jeremy gave in use in churches across the country and the world. As you say, you have moved away from the church, so you would seem not to know the developments that have occurred within the liturgy, versions of the Bible, etc. over the years.
More generally, its worth noting that the Greek word that is translated 'lead' (in the AV and some other older versions) in the two forms of the prayer we have, was interpreted as meaning 'protect us from' as far back as many of the Early Church Fathers.