The question was about whether First Gold might work in MY bitter recipe.Yep. Challenger and First gold work well together.
While I doff my cap to Mr H on recommending fuggles, there are other options available.
I did a "Lakeland Ale" with challenger and First Gold in 2020 that was very well received by all who tried it (including some old farts that are quite hard to please). It was somewhat representative of an English Lakes / West Yorkshire amber bitter. Quite different to Hazelwood's preferred Southern English bitters, but still an excellent ale. Go with a Yorkshire ale yeast for this one. I used Nottingham which was ok but suppressed some of the hop flavour - it could have been brighter. Challenger for bittering, challenger and First gold in conservative measures for aroma and flavour. The first gold tends to want to take over so you need a light hand.
NO!
(Only joking )