Is it structural rust likely to cause an MOT failure?
Does the hole interfere with any functionality, such as air intake or rain water direction?
Is it simply a cosmetic hole?
Is there evidence of any other rust issues, or this an isolated event caused as suggested by prolonged debris blockage?
Bodge mode (look away if offended
): Treat the rust thoroughly, particularly any signs of tracking to anywhere innacessible, then stick a patch of self-adhesive bitumin roof flashing over it. Then fit a new insulation board as suggested in place of the foam stuff.
Obviously negotiate a lower price, with a lot of tut-tutting