The DF700 does contain an electronics package (item 118 in EKAT), so it is not just a "dumb-motor" tool. The "pop" you heard may have been a destructive failure of the electronics module (bad power or other possible causes). Because this appears to be a sudden failure, it is less likely to be a failure of the motor itself (and that is good).
I do not know what the warranty requirements are for the UK, but this is certainly something to bring in for service. Even if it is not covered by warranty, the cost to replace the electronics module should not be too drastically expensive.