After doing a bit of thinky, I reckon that it's going to be easy to make the Bacon and Mushroom one. Cook off some chopped up bacon, onion and mushrooms, do some mixy mix with the cheapest cheese spread you can find, with some English Mustard. Et voila.That stuff was brilliant but an acquired taste. There's even a fan club who are now up in arms after Heinz stopped making the stuff a couple of years ago. Apart from toast the ham and cheese version was great for adding to scrambled eggs while cooking the using to fill a roll.
The ham and cheese version might be a bit more difficult to recreate because I can't find anywhere that sells lark's vomit.