Posted: 12/03/2014 at 18:06
Gravel or bark are probably the best options Adam. Strangely enough, gravel is often a lot cheaper than bark - especially if you get bog standard pea gravel. Bark gets dislodged more easily so it may not be so good next to the path, but it looks nicer unless you go for a better quality gravel, so it really comes down to your preferences and pocket!
If you don't want to grow anything else on the area you could put landscape fabric/membrane down first before putting the mulch on. It suppresses weed growth from underneath and will save you having to weed so much as you'll only get ones seeding in from above. Just make sure to leave a little gap round your existing plants if you use it, and ensure the plants aren't short of water first. DIY places stock rolls of membrane, but garden centres usually do it by the metre so that might be cheaper depending on how much you need.