This is my totally personal view on the topic I still hold after years of my enthusiastic interest in the English language.
When I first was trying to explain the issue to one of my students, I based my then thoughts on my practical reasoning only, without prior consulting a dictionary. I've thought that, since the verb be cannot be used with the preposition to, the verb that would nicely fit in place of be in such cases is go. Next, we went on to discuss the system of the tenses that could be used in such cases. Again, I arrived at the same valid conclusion that the only verb of the two in question that could easily be applied in such constructions is go (went to somewhere NOT was/were to somewhere) - in the case of the perfect tenses, have/has/had been to. And since the perfect simple tenses need a past participle to complete their meaning, to achieve the meaning of going there and back you actually need to use the verb go in its proper form, often followed by the preposition to (in the locative/goal sense) - so been (to) is the one.
That was years back. Now, I even feel stronger that such assumption of mine is really valid.
This is the first time I see anybody say that "been" is the past participle of "be" in
I've never been to London.
I've never tried to search for different opinions about it, so I may be misinformed, but I believe it's usually said to be the past participle of "go", at least in Polish classrooms.
So, BC, what is your personal opinion on 'been' being the past participle of 'go'?
I don't have one. I understand the usage and it's enough for me.
Actually, I never was a qualified teacher, I just had to (and later in time, loved to) do some teaching - they called me a private tutor of English. During my nearly-6-year experience in teaching English, I had the opportunity to provide tuition for around 40 people, from kids of 6 to grown-ups of 40.
But that was then, this is now - I'm not a teacher any more. Besides, it's safer for me to share my opinions and prescribe rules with that note (which I often forget to add prior to writing and submitting my posts ).
Leech (p40) joins in on the side of engee:
There are two perfect forms of the verb go: have + gone and have + been.
Leech, Geoffrey, (2004) Meaning and the English Verb, Harlow (3rd edn) , Pearson Longman
Michael Swan (p 95) lets me down:
Been is often used as a past participle of come and go.
Swan, Michael (1980) Practical English Usage (3rd ed, 2005), Oxford: OUP
I don't want to let you down even more, fivejedjon, but from the very beginning, I knew that the battle over this issue between you and me (or between the ones on your side and on mine) would be unfair.