You’re right — it is subjunctive, and should be “if I were to…”. Native speakers frequently fail to use the subjunctive mood — particularly in British English or in colloquial speech. Your example, which is so obviously subjunctive (I mean, he could have just said “if I wrote…”) strikes me as deliberately seeking a very casual or “folksy” effect (although it may not be that unusual in spoken UK English). Additionally, there are  colloquial versions of English that never use “were” at all — they always substitute “was” (this is particularly common in London English, if I’m not mistaken. You’ll also hear it on the US east coast).

By the way; in English, we say subjunctive mood, not "conjunctive."