Brownie
The entire Goldrush range was deleted over a year ago, if you have one I think I would be looking at the use by date.
Mabot's Ale was one of the standout beers in the Goldrush range, a dark amber with a very respectable bitterness and a nice hop taste addition.
I think the best substitute around would be Morgan's 'Royal Oak Amber Ale". Either would work well with a 1.5 Kg can of Amber malt and for me some Golding for extra taste.
In any case I would replace the yeast if you have a can of Mabot's.
MHB
(Mabot's Ale renamed from St Arnu, in memory of Dave Mabot - one of the good guys)