For the record, home/away averages for England's two best in the last 30 years or so:
PIETERSEN
Home: 52.75
Away: 44.16
Neutral: 11.16 (3 tests)
COOK
Home: 43.68
Away: 45.64
Neutral: 55.36 (6 tests)
Safe to say the "batting in English conditions is difficult so our players average much lower overall as a result" stuff is bollocks.
Pietersen actually played a few MORE home tests than he did away, Cook played a lot more at home but his away average isn't significantly better to account for any difference had he played that many more away instead.
Now let's break down the "other top batsmen (who did happen to average above 50 during this period) padded their stats vs **** teams". Although they didn't play as many tests vs Zimbabwe (none) and Bangladesh, they did play plenty against West Indies, who weren't much better. Here is what the two average vs them:
PIETERSEN
Bangladesh - 68.40 in 4 tests
West Indies - 56.20 in 14 tests
COOK
Bangladesh - 49.00 in 6 tests
West Indies - 57.96 in 20 tests
Again, safe to say that if you took these out of their standings, their averages would drop EVEN further. You can't just take out averages for one set (the ones who averaged > 50) and then not take them out for the ones who didn't.
Edit: Interestingly enough, Dravid only averages 38.67 in 33 tests vs Australia, and 33.83 in 21 tests vs South Africa (29.71 in 11 tests IN South Africa) which are very, very poor records for a player of his calibre. Didn't realise that. While I still think he's a top player, there were clearly chinks in his armour. And the suggestion that he was (overall) a better bat than Sachin Tendulkar is, quite frankly, ludicrous.
It's also worth noting that for a few of the players, the Zimbabwe sides they played against (early 90s to late 90s certainly) were arguably a better team than both Bangladesh and West Indies currently are. They had Andy Flower and Heath Streatk, for starters. The rest of the team (bar Houghton) may have largely been ****, but they still had a few capable players. Andy Flower is arguably a better bat than any English bat since the 90s.