Hi baggy I'm new here too and to keeping rcs.
My first bit of advice is unfortunately from bad experience, but it's worth sharing, especially with people in UK. Be very careful where you get your plants from. If they're coming from Asia, there's a real risk of insecticides/chemicals that could harm your shrimp. I understand that plants shipped from the Netherlands are a much safer bet(?) . Maybe ask your supplier where the plants come from? I won't buy from Asia again.
My tap water contains nitrite, something regular water conditioners don't deal with. If your not using tap, then ignore this, but worth a 2 minute test if you are
You might also consider running the tank for a few weeks once you have your filter in. This allows the biofilm to build up. Your shrimps will appreciate this. In fact I think a month is preferred.
Other things to consider buying at some point are Indian almond leaves, cholla wood and a small feeding bowl. The feeding bowl stops half eaten shrimp pellets getting down into your substrate. The leaves and wood are popular with the shrimps (usually).
Good luck with your tank, these shrimp are great pets