This function is indeed faster than CONV, but as soon as I attempted to use it on larger data sets, Matlab produced an 'out of memory' error, whereas CONV can cope just fine with the same datasets (albeit taking longer).
FYI if I run the 'memory' command my output is as follows:
Maximum possible array: 11862 MB (1.244e+10 bytes) *
Memory available for all arrays: 11862 MB (1.244e+10 bytes) *
Memory used by MATLAB: 820 MB (8.597e+08 bytes)
Physical Memory (RAM): 8011 MB (8.400e+09 bytes)