Hello
Ordnance Survey maps show that the street was being laid out but didn't yet have buildings on in 1884, and was largely complete by 1901. Council planning departments have plans for buildings built since the modern town planning system came into being in 1948, which is therefore too late for this street.
Bedfordshire Archives does have a document (CDE57) described as "Plan of Bower Building Estate" from 1881, which apparently covered Howbury Street. The description suggests this relates to the sale of the land and probably wouldn't have house plans included, although may still be of interest.
Bedfordshire Archives' catalogue also lists some later sales particulars of houses on the street - it's possible (but by no means guaranteed) that they could have plans amongst them.
Another thing to consider is that Bedford Borough Council's planning department should have plans any of planning applications submitted for specific properties on the street since 1947. Many of the more recent applications should be searchable on their website. From such plans you may be able to deduce what the original layouts were.
Good luck.
