It is a nice assortment of weapons, just not my sort of thing
.204 is a very quick round, is that range legal for Altcar? I thought it was an MoD estates run range so capped to 1000m/sec The idea of shooting 5mm is apealing if you are looking to shoot something different but I am not sure how accurate the .204 is.
.223 or 5.56x45 is a lightweight for longer stuff and tends to fall over at 600m plus, you can use the same calibre bullet (.224) with a larger case to throw 80/90 grain stuff but the only person I know doing that is my wife with a 22-6.5X47 wildcat that sits at just under 1000m/sec and is good for accurate 1000m+ stuff. No doubt others do similar but I havent met them.
7,62x51 is fine, for the UK I mostly shoot an Accuracy International, boring at 600/800m and fun at 1200.
For truly accurate (sub MOA) stuff beyond 1200 needs a different outlook on life.
At least you are in the right part of the world if Altcar is local and you have Diggle in the East (take a coat)
Enjoy!