Either of those are fine. There are subtle differences, but they are mostly very similar. British base malts are generally a tad richer and sweeter in character. Golden Promise is a bit sweeter than the others, so be cautious about using too much of it.
I generally find that a American 2-row or Pearl Malt base accompanied by rye, wheat, or vienna works best for my tastes. Sometimes I toss in some light caramel malt and corn sugar.
I really don't like toasty, bready, sweet grains in my IIPAs. The hop character is destroyed once you start using a lot of Munich, overdoing it with crystal malt, using Melanoidin or Victory, or fermenting with a yeast that accentuates maltiness.