The dual-licence route would help with Ryanair (although they seem to have their own training programmes), SAS's LHR base, some corporate operators, plus specialist companies like 2Excel and DEA Aviation. If you're happy to live and work in Ireland it opens up Aer Lingus, ASL, Emerald Airways' Irish AOC and possibly a few others.
EASA in the UK adds a few thousand pounds but it's not like you have to do everything twice. Apart from the likes of FTE Jerez, I don't know of many places that do dual-licence training abroad.
As for the UK, the tricky bit is finding a modular training school which isn't at the other end of the country, options are as follows:
Stapleford: I did hear though that dual-licence training was under review there due to cost and the option to train part-time appears somewhat limited, I believe most of their students are full-time.
British Aerobatic Academy: Generally focused on aerobatics but they do dual CPL/ME/IR. Grass airfield with no ILS so MEIR with low vis etc. would be a challenge and I believe they only have one twin.
Aviation South West: Maltese licence, I'm not entirely sure how that would mesh with Austro Control exams, assuming you've sat Austro Control exams of course.
Flight Training London: The last time I spoke to them only the ME/IR was EASA-approved so you'd have to do the CPL elsewhere, could end up falling foul of BA's Max 3 ATOs rule (assuming it still exists).
ACS Perth: Great if you live in Scotland but otherwise a bit far.
Ravenair: I've heard the waiting list is very long.
Leading Edge: Not many people on here have positive things to say.
The other option of course is to do CAA-only flight training and get 1500 hours, though you might have to resit some EASA exams if you can't get those hours in three years.
If any info I've posted here is incorrect or outdated, please feel free to correct me. Likewise, I'd be interested to know what other people's views are since I'm in a not hugely dissimilar position to the OP but cost isn't an issue and I don't have family commitments.