im not familiar with that boiler and cannot find a picture of it on the net.
usually with room sealed boilers, the outer casing is for decoration and then there is an inner casing which provides the safety seal against fumes entering the room.
is this the case with your boiler? are you sure the hole is in the outer case and not the inner?
the gas safety regs have gone a bit mad of late. it appears that lets say you had a room sealed boiler and the seal had failed and that part was obsolete. you could have gone and bought some foam seal for a fiver and fixed it, now you can't repair any boiler with any part not approved by the manufacturer, so for the sake of a �5 bit of foam you have to fork out �2000 for a new boiler instead.
your best bet is to contact ideal and make sure the part is obsolete and ask them for their advice on what could be done. you could also get a second opinion from a different engineer.
p.s. if you do need a new boiler don't get an ideal !