Paint Defect

[scottiedog]

There's an unusual paint defect on the roof of my MK8 Fiesta. It's a straight line about 2-3mm wide from one side to the other & appears to be under the laquer in the paint. The laquer was blistered along the line but wet flatting with 2500 wet/dry sorted that out, laquer now smooth. The defect is still visible & looks like the paint has sunk along the line. A local bodyshop think the roof has been partially resprayed but not blown in properly & now needs completely respraying at a cost of about £150.

Is there a way of repairing this defect without resorting to a full roof respray? Any advice welcome, thanks in advance.