253? do you mean 153? i dont know what unit of measure they're giving you, since snowboards are metric and you're in england and on metric anyways...
lets say for simple sake that you meant 153, 156, and 158.
there isnt going to be much difference. just make sure of the side cut. make sure it fits your boot
without too much drag on either side. thats the most important part.
as far as the length between the 3, unless you're...lets say 5'4, all 3 of those board are pretty
much in your range. the 158 is going to be the faster of the 3, and in my opinion more responsive
(i know a bunch of sites say shorter boards turn easier, but i dont believe this, my 156 turns better
than my 146) the 153 is the slower, and is easier to control, mostly because it wont flex as much
so when you turn your board is bending in the same weight on both sides, instead of a longer one
which the nose could carve out more on one side than the other, depending on conditions (say
you hit an ice patch). and the 156 is kind of the compromise.
and when i checked the currancy converter today, thats a super deal at aliltle more than $150 for everything.
if you can go to a resort, try renting one of all 3. most resorts will let you swap out sizes as much as you want.
and as you progress, you'll find different sizes work best for different things you want to do.
(ie, the 153 has a lower swing rate, making it easier for spin tricks, while most people i know like longer
boards for rails for the extended flex pattern).
if this is your first board, you're in your target height if the waist is wide enough. 9/10 you'll trash your first
snowboard to death learning everything. so find the one thats the easiest to ride NOW, and save up for
when you hit intermediate and know what you like to hit most of all.
hope that helps!