I think that it's pretty clear on the Grenson site where the different lines are made.
I think it also depends on what kind of shoe you are looking for too. I have a pair of the Indian-made Grenson Curts that I bought last year as a winter shoe because of the commando sole. They are lovely shoes, comfortable and extremely sturdy - perfect for what I wanted them for and I paid a very reasonable £150 for them. They still look like new and I'll be wearing them 3-4 days a week this winter too.
However, this summer i had to buy some Oxford-style shoes for weddings etc and decided that after looking at them again, the quality of the Indian-made Grensons just wasn't up to scratch for a 'proper' suit shoe and certainly not a patch on the Church's I was replacing. They construction and finish just wasn't refined enough to justify the price tag in this particular instance.
In the end I couldn't justify spending nearly £400 on a pair of shoes I wear 3/4 times a year at the moment, so I bought some Loakes - which were a good compromise of price and quality.