Ok. Thanks.
I do feel that I am reasonably placed to understand the needs of people with reduced mobility because although I am lucky enough not to be in that position myself, it is part of my day-to-day job to try and consider these things in some detail from a design point of view.
Lots of things that individually seem insignificant, placed in people's way, add up to an environment which becomes difficult for some people to navigate. Furthermore, the less consistency there is, the worse everything works. It's not just people who are in wheelchairs but, amongst many others, those who are visually impaired too. There is a lot of guidance on how to design street furniture and the interior of buildings that is based on research into what makes things difficult for people and some of these things aren't things that you'd necessarily think of. For example, if there's an information board on a pavement that's supported on two posts, there should be something between the posts at low level because someone blind or partially sighted will be scanning the ground at low level and might not notice the fact that there's a board at head height spanning between those two posts.
I constantly see people blocking the pavement with all sorts of things including parked cars and because I have an eye out for it I notice it when I see, for example, someone elderly having to go out into the carriageway because of this. When there are roadworks in the pavement, there are (supposed to be) safe routes provided around it with barriers so drivers know that people will be walking there, and there should be those yellow kerb ramps too, for people who find it difficult to get over kerbs. This is not health and safety gone mad, it's all for a good reason.
There's no reason why this section of pavement should be subject to special rules.
It's not acceptable in any context where accessibility is being discussed to use the reasoning that it's ok because only very few people with mobility problems might want to use a certain area, because that misses the whole point about universal accessibility. It doesn't matter whether it's two or two hundred wheelchair users per year who might want to head down the pavement of that alleyway. There has to be a good reason to decide it's ok to knowingly exclude those people or make it more difficult for them.
I am not saying SWU or any of the people who made the objects did so with any intention to block accessibility. However, if it's pointed out to Lambeth then it's their duty to sort it out.