Previous research into the use of what as a relative particle has revealed it to be a predominant feature in parts of the Southeast and the Eastern Midlands (Orton et al. 1978).
Converting the acceptability ratings into a 5-point scale from 0-100, we find the highest average rating in northern dialect regions (69), with an incremental decline moving southwards (midlands – 64, south – 51). Speakers in Northern Ireland, Wales, and Scotland all seem to evaluate this sentence in a similar manner to those southern dialect regions, with average ratings of 52, 53, and 55, respectively. Clearly, then, this is another syntactic construction favoured in the north of England, although the effect isn’t particularly strong here.