I'll avoid mixed use lanes as much as possible because of the hazard they present to pedestrians, and because they're usually more of an inconvenience than an aid to cyclists. But if I do use them, I'll always give way to pedestrians.
There is one in my area that I like using - it's about a mile long and runs down the shoreline. I prefer it to the road because it's much more scenic and is totally free of motorised traffic. But it's also popular with walkers, joggers and dogwalkers. And although it's divided by a solid white line, you have to accept that other users aren't always looking out for cyclists despite the frequent markings on the cycling side. The majority of people will move over if they see you coming but, you get the odd ones who'll wait until you're almost in their face before yielding, and the stubborn ones who won't move over at all. I find dog walkers are the same though they don't always take control of their dogs, but these...
It drives me mad, when dog walkers can see you coming, but keep the lead on the full extension, with them on one side the path & the hound the other, making no attempt to pull the dog in or move over .. That to me is just damn plain rude & totaly dangerous for both the the cyclist & the dog.
... don't even get me started. There's two women I see regularly walking a dog, and one of 'em will always walk on the cycle side just for the hell of it, dog-lead full extended, and she scowls at me every time I pass!!! WTF?
In all fairness though, I doubt if most people are aware that the Highway Code advises they should keep to the pedestrian side. It might help if the Local Authority put up signs that politely ask pedestrians to keep to one side, but I've just come to accept that this route will always be slower, and when it's sunny and there's a lot of people about I bite the bullet and use the nearby roads instead.