From their site:
Simpsons Golden Promise
Golden Promise, an early-maturing spring barley, is the Scottish equivalent of Maris Otter. Though brewers north of the English border claim that its sweet, clean flavor is superior to Maris Otter. Golden Promise malt has a depth of flavor that makes it the ideal base malt for both UK and USA-style IPAs. Golden Promise is also used extensively by premium whisky distilleries such as The Macallan.
Yeah Maris Otter looks like a good substitute. Chimone beat me to it.
Once the wind has been broken, it cannot be fixed.