As a self taught Excel user I appear to have developed a personal style that
differs from most examples of spreadsheets that I see.

One issue is the use of named ranges. I observe that I rarely use
expressions such as
= L9 * "Master sheet"!$F$15 / 100 ,
prefering instead to name all variable and arrays
= Sales * VATrate / 100.

Would professional users regard this as good practice or are there drawbacks?

To take this further, I tend to use array formulae wherever appropriate.
Again I find
{=spectrum*displacement^2} ,
in every row, far more readable (and hence less prone to error) than
="standard spectra"!$B13 * $C15^2
with the usual variation row by row.

Here I can see a downside though. Whilst array formulae do discourage end
users from tampering with the workbook, they are a pain to resize to
incorporate more invoice records or increased frequency ranges.

Again I would be interested in the opinion of others.