I am suprised by the lack of enthusiasm for a move to BA. If you do seriously want to consider a change then I would recommend you consider BA.
I dont think there is a flying career in the uk at the moment that will provide for you the security, lifestyle, career options, long term earnings, variety that BA will.
I started in Ryanair and jumped to BA as soon as I could (2005) Granted I may be looking at the company with rose tinted spectacles sitting on the 777 but I have to say I love my career.
If you joined on SH you would probably be there for about 6 years before getting LH but then its nice to have the choice to suit your lifestyle requirements.
I think the pp34 change should not be the deal breaker you seem to think it is.
Also my understanding is that BMI integration would provide for better long term career progression as BA will find itself with the opportunity to grow at LHR and transfer slots to LH if required.
At the moment a LH fO starts on a basic of about £49,000 this increases at
about £2600 per year
With the new PP34 I assume you would still start on £49,000 but take extra 10 years to reach the top, this would be an annual increment of £1800.
So £2600 v £1800 or £800 per annum gross difference is not a huge amount. Please bear in mind your pensionable salary will be the same as it currently is for BARP pilots in BA so your pension will be no worse.
I dont think BA have ever carried out compulsary redundancies. My friend in VA has faced it twice in 4 years and has been forced to change base and aircraft type. The 750 hour VA limit is also a red herring as BA pilots probably average between 750-800 anyway.
Best of luck deciding what you do.