It's perfectly possible to get an economy seat on a segment despite a business fare - the fare is LON-ALC not LON-MAD-ALC and will use Y if there is no space in J on a particular leg. This will have been disclosed in the booking process, but it probably could be more obvious. There's no discount if this happens, because the fare is the same rather than being constructed leg-by-leg - but you should be able to cancel within 24 hours. Don't keep it in the hope of getting "put back in business" later - you will be told this is what you bought (and it is).