Not a valid value for 'QName' in Inline XBRL for the UK FRC taxonomy

I think the error is referring to the content of the xbrldi:explicitMember element, which is empty. It needs to be filled with the qualified name (QName) of the member that you wish to associate with the bus:AccountsTypeDimension axis.

bus:SomeValueAccountsTypeMember

Some of the options I see in the online taxonomy viewer (look for "6029 - Dimension - Accounts type" in the viewer) are:

bus:FullAccounts
bus:FilletedAccounts
bus:AbridgedAccounts
bus:Branch
bus:Foreign
bus:Subsidiary

The way to think about the context is that it is a set of key-value pairs that associates members with axes (also known as aspects, dimensions...), in your case, a logical view that one would get in a user interface looking at the logical context of the ix:nonNumeric element in the provided snippet would be:

In other words, these are the coordinates of a cell in a big data cube, and that cell contains the reported fact value.

The concept (which is in the name attribute of ix:nonNumeric) is also part of the (logical) context as shown above. For numbers with a unit, the unit is also considered an aspect even though it is syntactically separated from the context. It is a detail of the XML syntax but in the JSON/CSV syntaxes the concept and unit appear alongside the other aspects.

Also there is a typo further down, a closing double quote is missing, and the element is not closed:

some value here