I have a 10 sector TP run coming up later this year that is starting/ending in DUB.

I've now had some flight changes come through but cannot accept/amend the changes online but I am asked to call BA to confirm or amend the suggested changes.

As mentioned I cannot adjust the flights online, so before I call BA I wanted to be sure I know what I am allowed to do so I can prepare how to approach the call and what to say if they suggest my changes aren't allowed (if indeed they should be allowed).

The flights that got changed are the AA flights and the flights I want to change are the BA flights.

Here's what I'd like to do:

Move the first and last flight of the trip (DUB-LHR & LHR-DUB) so that they are either together at the front or at the end of the trip and away from the main trip, so that I can fly the trip to/from LHR and do the DUB leg at some other weekend either before/after the main trip to the US and without needing buy extra flights to get me to/from DUB.

My question is:

As the ticket was issues as a "to/from Ireland" ticket I wanted to ask if it was possible to change where the trip starts/ends and the 'order of the flights' e.g. if I do the change as suggested above it would start in the UK and end in Ireland (or vice versa) and not be in the 'order' it was initially booked in.

Or perhaps, to frame the question more generally:

Are there (what are) the restrictions to which changes one can make when a flight has been cancelled in a multi leg and multi airline trip on a BA ticket?

Thank you for your help everyone.