I can see where you are coming from. I am no by no means an expert on military uniforms, but there is a fairly noticeable difference between First and Second World War British Uniforms.
Webbing- In Ww1, pattern 1908 webbing was primarily used, consisting of many short ammunition pouches, as opposed to the Pattern 37 webbing used in Ww2, which features only 2 very large, oblong ammunition pouches, as seen in this song.
Helmet- I believe they did use different models of helmet (Steel helm Mk 1, and 2 and what not) Though to an amateur like me, I cannot notice the difference.
Uniform-In terms of colour, First and Second World War British uniforms were similar. Different batches used different dyes, and the dyes looked different in certain lighting, from beige to brown to yellow to green to red. In terms of Uniform Pattern there is a noticeable difference, Ww2 Battledress features a short blouse, as opposed to the Ww1, hip-length tunic. Pockets were also placed differently on both the trousers and jacket.
Footwear- I believe there is some minor differences in terms of boots, though I'm not aware of the details of these differences. Where they differ most, is in the First World War, puttees were wrapped around the shins and calves, whereas in Ww2 ankle length gaiters/leggings were worn.
Thats about all I know in terms of general differences between First and Second World War British uniforms, I hope you learned something!