Those who pronounce spar and spa differently are said to have rhotic accents. Rhoticity was once a distinguishing feature of most Lancashire accents but is now rarely found. Wells proposes that it now only exists in areas north of Manchester, such as Preston, Accrington and Rochdale; occasionally in Northumberland; and along the coastline of Humberside and Lincolnshire (1982: 368).
There are no signs of obvious rhoticity in areas just north of Manchester. In fact, a mere 12% of speakers from the North West pronounce these words differently, a figure comparable to all other regions throughout England. The only accents exhibiting rhoticity (those where spar and spa are not homophonous) are found in Northern Ireland (93%) and Scotland (79%).