Retail or wholesale?
Wholesale, as an MCS installer just login to Segen's portal and you can do you own quote / estimate your self.
Retail, what do you mean by mounting system? What roof type, what angle, what colour, which panel, which orientation, how many rows, how many columns, ...
If you're after it for your community hall, you'll need more than mounting, you'll need inverters, wiring isolators, etc etc, the best thing to do is to ask a local installer for a budget price to supply and install the whole system.
Otherwise it's a bit like asking who much do a set of brake disks cost .. kind of irrelevant question when they need to be fitted by an expert...
It's like the guy who charged £500 for fixing the motor by hitting it with a hammer, £1 for hitting it £499 for knowing where and how hard to hit it.
The £1 is an irrelevant figure.