I suspect the main issue is pricing, which is slightly on the higher side for both the area and the overall scale of the property. A five-bedroom home in the local area sold for £385,000 less than a year ago.
The additional spaces such as the office, utility room and snug will be very appealing to many buyers, however, these appear to have come at the expense of overall room proportions now being quite small. As a result, the property is likely to only suit a family with young children, effectively functioning as a three bedroom home with a fourth room as a bonus rather than a full-sized four-bedroom family house. I also think it wouldn't suit a family with lets say 2+ teenagers. Because of these limitations, I would expect buyers to compare it more directly with three bed properties in the area.
In my opinion, a more realistic price to generate interest and achieve a sale would be “offers over £350k”. It is likely to attract a specific buyer who values the layout and may stretch to around £370,000 if they see it as the right fit (I personally would if I was moving to Swindon!)
Out of curiosity, why are you looking to move?