Green Frogs & Hybridisation

A friend of mine recently bought a reptile & amphibian book that states that Edible, Pool and Marsh frog can be found in East Yorkshire. I know of the Tophill Low frogs, which I thought were Marsh frogs, but not of the other two species. I contacted the warden, and was told that they were usually described as 'Marsh Frogs' or 'hybrid Marsh Frogs'.

Now, I have recently been reading about how Edible frogs are produced and how they persist, and I just wondered if anyone on here could tell me whether I have got the right end of the stick.

According to what I was reading, Pool Frogs and Marsh Frogs can hybridise to produce Edible Frogs. Edible Frogs cannot hybridise with other Edible Frogs as the offspring are usually malformed and do not survive to adulthood. Therefore, Edible Frogs have to breed with either of the parent species.

Now, Edible Frogs are odd, in that when they create sex cells, they only contain DNA from one of the parent species, the Marsh Frog (the Pool Frog DNA being lost somehow). Thus, if an Edible Frog was to hybridise with a Pool Frog, the Pool Frog would just receive Marsh Frog DNA, and, as such, another batch of Edible Frogs would be produced (I think!). Therefore, it seems to follow that if a Marsh Frog was to hybridise with an Edible Frog, the Marsh Frog would only receive Marsh Frog DNA from the Edible Frog, and as such the next generation would be back to pure Marsh Frog.

From what I have read, the above seems a roughly accurate account, except for the bit about Edible Frogs persisting in Pool Frog populations, and disappearing in Marsh Frog populations, which are my own deductions that seem to follow logically on. 

I would like it, however, if someone on here who knows more than me could confirm that I am accurate about the reproduction of Edible Frog with the parent species, and if my deductions about Edible Frogs persisting/dying out in either population of the parent species seems accurate.

I understand now why the situation in the wild is so much more complex. Wouldn't mind seeing a scan if you can manage it.