Hughes et al. propose that, given its intermediate location between the South West and South East, Southampton features an accent with very distinctive Southern qualities; this is expressed by, amongst other things, a neutralisation of vowels preceding the consonant /l/ (2012: 90). This leads to words like fool, full and fall all possessing the same vowel and therefore being homophonous in this accent.
Other than a few speakers dotted around Sheffield and Mansfield just to the south, full-fall homophony is not an obvious feature of any accent. Despite Hughes et al.’s (2012) grouping fool, full and fall together, they seem to be distributed slightly differently throughout the UK. Contrary to what was found with fool-full, full-fall homophony isn’t present at all in Northern Ireland, and only with one speaker in Scotland.