Nearly two months after I made my enquiry I have had a response from Guinness.Nigel wrote: For reasons that I will reveal in another post shortly, a few weeks ago I formally asked Guinness about the legitimacy of a Saturday record attempt, and also for confirmation of the status of Olympia and how it has to be visited given the current situation. Other than an automated response acknowledging that they have received my query, I've not yet had a response. I'm not not holding my breath expecting a speedy (or necessarily sensible) reply.
They have confirmed that attempts must be made on a weekday not a weekend. The reason given being that "all record attempts are undertaken under identical conditions so that the results of any two attempts at a given record title may be compared". Obviously this is nonsense as when the previous record was set there was an all day 20 minute frequency for the Olympia shuttle, as there is on Saturdays now, but not on weekdays.
In response to my question about what would happen if the Olympia shuttle were only to run at weekends they said that "since the current record holder planned their attempt in order to ensure that it was possible to visit Olympia, any future attempt must also do so". Adding rather patronisingly that "planning is part of the challenge which must be carried out before the record attempt takes place". So they have not actually answered the query about how you would do Olympia if the weekday service were to be completely withdrawn.
None of this this affects my next planned attempt on Saturday 25 August, which I'm still intending to do. What it does do is confirm my opinion that GWR do not understand this record and are probably not fit to adjudicate properly on attempts.