I have tried a couple of times to charge my Spark via USB cable plugged into my laptop.It doesn't work at all for me.  Is this normal?  I haven't tried a power bank, but will it only charge from a wall charger?

I think this is normal, because USB ports on computers (Mac and PCs) can't supply the proper amount of current required to charge the Spark's high capacity batteries. I once tried to charge my Spark using a powerbank, and this didn't really work - the Spark drained it completely and the powerbank got very hot. I'd suggest you only charge the Spark's batteries using either the official DJI Fly More Combo's 3-battery charger of the official DJI wall/travel charger.

Good quality USB power banks do work quite well with Spark. Be sure to get one that supports Quick Charge to get shorter charging times (the same applies to third party USB wall chargers).

cheers guys for the replies
actually the quick charge thing makes sense, i've been using my iPad charger and found it has been nowhere near the touted 1hr20 but that is a few years old.  must use my HTC charger and see if there is much difference

unfortunately i didn't buy the combo so only have the option to plug in via the usb cable

It is still recommended to use the original charger as DJI does not take any responsibility for the damage caused by third-party battery chargers.