E46 stonechip / rust problem !

[j.d.clarke]

Any ideas on this anyone ?

I have a 1999 'V' 328Ci in Black. As with most vehicles I have managed to pick up some front end stonechips over the years. Unfortunately (my fault entirely) one of them has now developed into a 1.5 inch square area of bubbled rust under the paint near the front edge of the bonnet. BMW have quoted £515.00 to remove / respray and refit the bonnet !

Any ideas on other options ? Will ChipsAway (or similar) be able to deal with this or am I going to have to get a full spray ?