Cathay Pacific Asia Miles - Mixing "B" and lower subclasses

May I ask for your wisdom. I've booked LHR-HKG. I have booked mixture of "B" and "M" subclasses, but I was told by London ticket office that because "B" is a published fare it couldn't be mixed with "M" class. Usually, mixing of "K" or "H" et. al. is not a problem, but I didn't realize "B" and "lower" can't be mixed together. Is this true? Price of purely "M" is 850GBP and purely "B" is 1350GBP so I hoped I had somewhere in between.

any exerts on ticket rules?

You can have mixed fare classes if both fare rules allow it.

In your case, if the fare rules for both the B fare and M fare allow mixed classes, then you are fine. You need to look into the fare rules. Generally speaking, YBHK fares allow mixed classes, not lower classes. There are exceptions, you need to check.

Exactly, You can't jsut expect to mix classes to suit yourself with out the fare rules to support it.

Just because you can make a B and M or whatever class does not mean anything until it is ticketed, and for that to happen you will need a set of corrosponding fare rules.

Therefore when people keep on asking, is there an I Class available, it is actually quite useless unless there is a set of I Class fare rules.

I booked an ex-LHR V+K ticket (LHR-HKG-LHR) successfully in 2005.

According to the condition of Round Year Fare (a TA in London China Town),mixed class is permitted at half return levels. In all cases,the lowest booking class rules apply.

thanks for all input so far. so far my problem is to fly on the day i wish (price is the secondary issue here...)

looking at fare rules doesn't really reveal anything excitingly new, unfortunately

Can you confirm B and waitlist M? If you have OW status, that will give you priority and you can see if that can be cleared before the ticketing deadline.

If you are MPC Gold and above, you can do a seat guaratee on M.

at the end, I decided to route myself via continental europe. The CX flights are dead full (and I mean I can't even book Y) in the preferred dates in Dec. Amazing how well the load is. It's like a guranteed op-up flight on A346, shame I couldn't get myself confirmed.

A flight from LHR-HKG return on "B" was 1400 GBP, whereas I fly from CDG-HKG return on "L" was 620 GBP. Even I pay for BA flight return to Paris, that's only an additional 120 quid. I guess I gotmyself a good deal afterall...

and no I'm only making Gold during my trip thus technically speaking I could squeeze myself on any flight on my way back...

I am not comtemplating whether or not should I go buy a cheap Y Class tix instead of I Class ex TPE next year in Jan for my return trip to LHR. Since it is almost 95% guarantee you will be opup to J anyway as a DM! and I can get guarantee seating in most of the discounted Y Class.
Just wondering how much is HKG-LHR 1 year tix in the cheapest CLUB MILES earnable Y Class.