Ok I can give you the low down on all things Marmite and Vegemite, lol. I loved Marmite when I was younger and still eat it occasionally. Just an FYI, Marmite produced in the UK is Gluten Free but otherwise you need to be careful. Vegemite is not Gluten Free so you wouldn't be able to eat it anyway.
Because we've a lot of Aussie's living in Ireland you can buy Vegemite very easily here. There is definitely a difference in the taste of the two, with Vegemite not being as strong.
However, the secret to eating Marmite is to literally smear a very small piece on bread/crackers etc. If you spread it like you would jam, your mouth will probably close up from the shock.
Marmite is packed with complex B vitamins which are very good for you, but it also has a lot of sodium in it and as such you should take it sparingly if you need to watch your sodium levels.
To recap:
If you spread it like this, your taste buds will probably up and leave you:
Spread it like this and they will remain your friend:
Barb, I'm afraid you can blame your Irish gene's on this. Ireland has one of the highest prevalence of Coeliac Disease in the world.