Very smart.. obviously dicntnya.. but how did you get to species?
Matt - image search in the first place to get me on track, read text in Collins Spiders, and then had a look at the epigyne under the microscope, though this can be a bit subjective for someone who hasn't seen lots of either likely species I must say. Found this up in a hedgerow, rather than lower down on flowering plants though I'm sure that's not conclusive. SRS website shows both uncinata and arundinacae likely in VC55, though there are more dots for uncinata generally and in my hectad.
Fair do's. I was hoping you weren't just going on general appearance as, unless your Mr Merret, only the heathland dictnya latens can be reliably seperated this way. Female dictnya are at the harder end of spider id as they have very little structure to the epigyne, and you probably had to look for the internal structures which is just about doable - but a lot easier to see if cleared. The males are much easier, and usually they are paired up so if you find one the other isn't far away.