You have been given some great advice so far....
I have re-read your posts and just want to raise the following...
1) You say Ash has started growling and then bit your MIL - he is growling to say he is uncomfortable with something (this is the only way a dog has to say "Back Off") so you need to find out what is causing the growl... did he growl before he bit?? Where was he when your MIL bent over to kiss your OH goodnight?? A human leaning over is very very intimidating to a dog, so he may not have been "guarding" your OH, but rather responding to a the perceived threat of your MIL leaning over him.
2) You say Coco has "tendencies towards Cocker Rage" - I would get that out of your head straight away - Coco may well have longer standing behavioural problems that you have been able to manage, but Cocker Rage is extremely rare, but can be a very serious issue - it's not something that comes and goes. Some vets seem to like to "diagnose" Rage at the drop of a hat but in reality there is a strict set of criteria which would need to be met before Rage should be even considered...
3) You asked whether Ash is confused about who is "leader of the pack" - this sounds like you are looking to pack theory/dominance to solve your problems - this is being increasingly discreditted by modern dog trainers (and can cause more problems than it causes). It may be that, with so many adults in a house, not everyone is being consistent about reinforcing boundaries... that's not a "pack leader" issue, just a consistency issue.
As others have said, you really need to get a behaviourist in to see what is causing the growling, so that you can address the cause... however your options do seem to be limited and if the contact Jane and Trevor have found uses negative methods, I wouldn't touch it with a barge pole. Try and get hold of some books (or search the internet) to find info on canine body language and positive training methods. One of the key causes of behavioural issues is something as simple of lack of consistency (not saying that this is the case but improving consistency is certainly not going to cause more problems!) - make sure everyone in the house is using the same responses to the same situations. Avoid confrontation and try to find solutions to potential problems before they arise - if a dog always growls when someone sits down next to them on the sofa I would either put a "no sofa" rule in place (spending a lot of time positively training the dog to learn the new rule), or simply ask the dog to get off the sofa prior to sitting down (and if need be train a reliable "off" command to allow this to happen). I most definately wouldn't continue to sit down next to the dog and tell it off for growling at me. (Again, I am not suggesting this is a cause of your problems, only demonstrating the problem solving routes to look at.)
As others have said, it is nigh on impossible to give good behavioural advice on specific issues over the internet, which is why I have tried to give some more general advice that you may help you learn more about your relationship with your dogs.
A couple of final points -
Don't tell a dog off for growling - simply walk away from it (while trying to see what the cause is).
If Ash is "bigger than your average cocker" and used to be a working dog, he may come from working lines rather than show lines, so mental stimulation will be very important to him - clicker training is great for tiring them out mentally, without over-exerting them in the heat you have there!
And don't underestimate the impact of the heat.... keep them clipped short, make sure them can paddle in cold water (the quickest way to cool a dog down is via their feet), freeze yoghurt and tuna, or other yummy treats, so that they have doggie ice lollies to help cool them down... Honey gets really really tired in the heat - and a tired dog tends to be a grumpier dog...
