Have a look at the new ICAO MPL - Multi Crew License.
It seems to be ideal for someone with a bunch of aviation experience. You get 240hrs training but they cut out most of the single engine hours building (enduring over a small lake in Florida). You still get around 70 hrs flying but the remaining time is in either the A320 or 737 simulator. You finish the course with much valued experience on a useful platform.
There's a fair amount of scepticism about a course with so few actual flying hrs, but as a Nav with bags of airmanship and multicrew experience you're already way ahead of the less experienced competition. It also won't allow you to fly commercially as a single pilot, you'll be stuck, initially, to a multi crew cockpit.
The MPL is, I think, only going to be offered as an 'integrated' course and won't actually be too much cheaper than the SOP £50-60k for a standard Integrated ATPL. One company, whose name I forget (but are an alliance of Astraeus and Bond Aviation), will be offering MPL training in the UK, India and the Phillipines, with the latter 2 options being much cheaper.
It may not be for you, but it's a course focussed on getting you into the rhs of a small airliner and therefore should be considered.