Thanks very much everyone for their input. The linked articles make interesting reading.

I will try and get some pictures if I find time here at work (ahem!). In the mean time, to qualify the appearence of the affected areas, the paint has a bubbled,blistered appearence rather than cracking in the finish. It feels rough to the touch, as if swelled by hard corrosion products formed beneath the paint.

cyccommute: yes the bike has been used throughout the winter on roads that are salt treated.

I'm expecting to find alumina type powdery deposits beneath the lifting paint. If this is the case, they will be capable of retaining moisture and salts that can contribute to electrolytic corrosion, allowing it to continue for some time after the rest of the bike has dried out.

It looks like my best plan is to assess the problem areas, make a decision on the integrity of the frame. Hopefully the condition will justify refinishing with appropriate prep and coatings.

thanks again,

Ed