Hi Aiden
I am still considering myself an starter as well so please remember what I will say its only my opinion.
I am from Uk as well so I am familiar with the products available and the prices asked for shrimp related products.My advice will be to try the Dennerle shrimp soil,its way cheaper than other shrimp soils and also its really stable for me(so far).I manage with it to keep an 19 litre aquarium stable with about 50 shrimp babies and 4 adults.Also I suggest to keep it simple with the filter and buy an sponge filter as they are extremly cheap and good for the shrimp.
Also try to buy the mironekuton powder as for me worked amazingly(I have shrimp for almost an year and didn't had one failed molting so far).
Thanks