Update to HTM64

Our latest reference article added to Notjusttaps summarises the latest NHS Estate Guidelines.
Although HTM64 is still relevant, this article sums up key requirements as specified by the latest NHS Estate Guidelines/ DOH Sanitary Assemblies
These guidelines do supersede HTM64 but in essence are much the same.
Hopefully readers will find that this cuts out much of the 'bumpf' and helps healthcare professionals understand what they need to know in order to make informed decisions when upgrading premises or selecting sanitary equipment.