Thanks for the warm welcomes!

I'd always wondered why flights show "I" availability right up until the day of the flight, even when it's impossible (for a mere mortal) to buy an I ticket so close to departure. Now I know!

Maybe this isn't possible to answer without taking a detailed look at the various fare rules, but assuming my TA only has access to the regular, published fares, was she "wrong" not to offer me the R fare?

It seems to me that if I'd have bought an R fare, and wanted to change, I could find myself in one of a few different situations:
- R+ availability on my "new" flight => pay £200
- D+ availability on my "new" flight => pay £200 + diff between R and D
- C+ availability on my "new" flight => pay £200 + diff between R and C
- J availability on my "new" flight => pay £200 + diff between R and J
(where, for example, D+ indicates availability in D, C, J but not I or R)

whereas, if I'd bought a C ticket and wanted to make a change, then I would only have to pay the £200 fee, unless there was only J availability on my chosen flight, in which case I'd pay the difference between a C and J fare as well.

So in the situation where there was R or D availability, and I had an R ticket, I'd pay less overall than if I'd bought a C ticket to start with.

When there's only C or J availability, I'm presumably no worse off upgrading my R ticket to C or J at the time of change than if I'd bought a C ticket to start with...

... or am I totally misunderstanding the "
CHANGES
BEFORE DEPARTURE
CHARGE GBP 200.00 FOR REISSUE/REVALIDATION.
...
WHEN THE ITINERARY RESULTS IN A HIGHER FARE THE
DIFFERENCE WILL BE COLLECTED - AND - THE CHANGE
FEE WILL BE APPLIED.
" in the fare rules?