I had some of this last summer when visiting another area and it was very 'orange forward', if there is such a thing, certainly for me. I thought it was a really enjoyable pint and went back for few more!Then it's likely orange peel with certain hops that I've had with marmalade beer in the past then. Guess it's wrong to assume as it had "marmalade" in the name that it contains actual marmalade over selected ingredients to give a marmalade flavour.
And in looking, my local home brew store does orange peel. So will definitely be getting some to try with an upcoming IPA. Though as a dry ingredient has anyone got any idea on how much dry weight to add to a 36-40 (ish) pint kit?.
Anyway the blurb seems to suggest it's down to the use of Amarillo hops.