I'm using this regex for some basic name validation
^[a-zA-Z][a-zA-Z]*([-' ][a-zA-Z][a-zA-Z]*)*$
However I'd like to also allow Mr & Mrs Bobble as valid. My current regex only allows a single space between character groups and I'm not sure how to allow <space>&<space> or <space>
You may use
^[a-zA-Z][a-zA-Z]*(?:(?: & |[-' ])[a-zA-Z][a-zA-Z]*)*$
^^^^^^^^^^^^^
See the regex demo
The non-capturing group (?: & |[-' ]) matches either a space, &, space or a -, ' or a single space. Non-capturing groups are used when the text they match won't be accessed after the match is found, so, in this case, all groups should be non-capturing: (?: & |[-' ]) groups two alternatives with the | alternation operator and (?:(?: & |[-' ])[a-zA-Z][a-zA-Z]*) groups a quantified sequence of patterns.
If you mean to match any whitespace, replace the literal spaces in the pattern with \s.