Well I dont think the articles should be merged but there are great difference between colloquial and standard grammar in other languages as well In German for example the difference is huge General features of colloquial German are almost complete avoidance of the genitive case loss of weak singular noun inflection avoidance of the simple past and the past subjunctive except for some frequent verbs complete loss of the present subjunctive and more Nevertheless there are no Grammars of Colloquial German There are just grammars and some of them have notes on colloquial usage I suppose that would work with Welsh too But lets leave it as it is