One of the key metrics which link the gas properties of galaxies to the star formation within them is the Kennicutt-Schmidt star formation law, a scaling relation between surface density of gas mass and of star formation rate. We present 850µm dust emission observations of a sample of 8 nearby spiral galaxies, made using the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT) as part of the JCMT Nearby Galaxies Legacy Survey (NGLS). We measure dust column densities, temperatures and opacity indices by fitting spectral energy distributions constructed from SCUBA-2 and archival Herschel observations, and used archival GALEX and Spitzer data to make maps of surface density of star formation. Comparing SCUBA-2-derived mass surface densities to star formation rate surface densities gives shallow star formation law indices within galaxies, with SCUBA-2-derived values typically being sub-linear and Herschel-derived values typically being broadly linear. This difference is likely due to the effects of atmospheric filtering on the SCUBA-2 data. Comparing the mean values of mass and star formation rate surface density for the galaxies in our sample returns a star formation law index broadly consistent with both the Kennicutt-Schmidt value of 1.4 and linearity. Our results show that a SCUBA-2 detection is a good predictor of star formation. We suggest that Herschel emission traces gas in regions which will form stars on timescales ~5-100 Myr, comparable to the star formation timescale traced by GALEX and Spitzer data, while SCUBA-2 preferentially traces the densest gas within these regions, which likely forms stars on shorter timescales.