My bitter recipe is this.
In a 23L batch I use 350g flaked barley and 250g medium crystal (150 EBC), then add pale malt to hit my desired gravity. My bitter is 1.040 so the percentages work out around 84% pale malt, 9% flaked barley, 7% crystal. I sometimes add 1% chocolate malt for colour.
I brew a clone of Orkney Corncrake for a mate which has extra pale malt added for 1.046 OG and the crystal is swapped to caramalt (or a similar 30 ebc crystal). I've also brewed it where I've swapped out 20% base malt for Munich or the last one was 10% imperial malt. So it's a fairly adaptable recipe.
For my 1.040 bitter it's 30 IBU, bittered with Admiral then 15g First Gold at 10 min and 20g at flameout for a 23L batch. I've mostly used Wyeast 1469 West Yorkshire but used Scottish ale yeasts for the Corncrake.
Hope your bitter has gone well.