Use the term 'Not of merchantable quality' when describing it. This means that not only can you expect a replacement/properly repaired and repainted tank, but should this not be forthcoming you also have the right to hand the bike back for a full refund. Filling the hole with clag does not constitute a proper repair any more than filling a tyre with foam repairs a puncture.
If the dealership is reputable they should source a used replacement tank under warranty, if not ask for your money back as the deal is not what they represented it to be. Also watch out for the replacement tank being 'free', but labour charges for fitting it coming to in excess of £100. That's another trick they often use.