The message
from "Dave Plowman (News)" contains these words:

Steven Briggs wrote:
Yeah had to cut mine down, although it is a low ceiling anyway.
Used a B&Q PP dremel clone, flexy shaft and cutting discs, as the
stainless is very thin & I didn't want to risk the distortion caused by
tin-snips or whatever.

A nibbler is ideal for this.
http://www.frost.co.uk/item_Detail.asp?productID=8006

But take precautions to collect all the chads. They're little crescent
shaped bits and they're right *******s if you get 'em in the carpet or
anywhere you're likely to walk with bare feet. Like little caltrops.

--
Skipweasel
Pay no attention to that man behind the curtain.