Have a connection at CMB, UL to UL ( BA Stock), any oneworld missconnect protection or benefits in linking the two PNRs?

No. Is not a OW benefit-policy. AA used to have protection, but from what I have read is no longer published.
As UL to UL flights it will be up to UL as what they may do/will not do. Keep your expectations realistic. {= having a credit card)
By BA stock do you mean a BA ticket number 125-xxxxxxx?
And you do not have a "connection". Just 1 flight ending and another that happens to start from the same airport.

Yes avios ticket on UL. OK, I have a 8 hour buffer. One does wonder what are the published benefits of these alliances which actually would help in need ?

8hr is a good buffer. With award flights harder to reschedule. May need *award* validity. Depends on the airline and even the staff processing the change (if they can)

There are no "published benefits" for separate PNRs and separate tickets. You get the standard benefits on each of those tickets, but they are - and will always remain - two separate tickets. You can never "engineer" them into a single connecting itinerary, having purchased them as two separate tickets.

Protection is, in general, intended only for passengers on connecting tickets.

There is no way to "link" separate PNRs that achieves the same outcome as having booked all that travel under a single reservation. ("linking" PNRs is effectively merely sticking a post-it note on the file - which may or may not ever be seen by anyone - and only informs the reader that there is a separate ticket that the customer wanted noted on the file; it does not get you, nor does it entitle you, to any of the benefits that you would receive if all flights were under a single PNR. It's effectively meaningless, but it seems that some airline agents acquiesce to the request, if only for an easy life and because it seems to satisfy the person asking for it to be done)

Precisely my point..these alliances dont seem to be of any help when most required. Suppose a friend in need..is not an oneworld ally indeed

To be clear, it is oneworld's policy to protect customers who have 2 separate tickets issued in the same PNR. If you have different PNRs you are out of luck, but this is not the case when you have 2 tickets in the same PNR. Usually, 2 tickets are 2 tickets as you said, but oneworld being an alliance does provide extra protection in this particular case if everything is in 1 PNR.