gaps in the brickwork

Blimey. What do you mean by 'gaps'

There should be no gaps blow ground, and its normal to let in proper rodent proof vents if you need ventilation.

well, maybe gaps is the wrong word. Every 5 bricks there's no mortar between the bricks so it looks like a gap.

There will be a tray dpc at that level built into the inner and outer skins of the wall. It is to catch any moisture in the cavity and drain it out through the holes you can see. It's probably not sensible to cover them.

That changes things then. I'm not a fan of it but if I were to put gravel down between the grass and the wall would that be alright? That might give enough drainage.

Ah. Thats odd though, because the main DPC is above that by two bricks?

Anyway, whilst its not SENSIBLE to cover them, IF you lay a shingle drain along the outside, an then cover THAT you ware probably no worse off.

I would personally risk that, yes.

Having seen what a good gravel filled trench that has some way of draining, itself, can do in terms of getting rid of water flung of gutterless thatched rooves, .another even BETTER option would be to excavate enough to put in a plastic perforated pipe, in gravel, and arrange for that to drain somewhere lower down.

Yes, but make sure it's large enough not to compact down into a solid or semi solid mass, 18mm pea gravel would probably be best, B&Q do some that is cheap as chips but looks OK when washed, sort of a purpleish colour....white limestone would also do but beware that it looks hideous when leaves and debris start making it go brown in patches.