If 10W think that we will always be expecting to go to the hold then he is mistaken. It is only entered in the FMS if (rarely) we think we are going there.
On the assumption you are inbound on a STAR routeing (as you will be unless you have negotiated a clearance to join direct outside the Airways CAS structure), what will be the terminal fix you have in front of you on your chart and presumably in the FMS as its your filed route, and what conditions apply to it in the absence of any ATC instruction otherwise (e.g information from EDI that you are being radar vectored for an ILS, Scottish can't clear you for an approach of course) ?
Will be interested to see if the AIP answer matches your expectations
250Kts or less 30 before NEW is pretty unbelievable to be honest mainly because the guys who do the speed control and sequnces don't work (or look) that far out and many who work that airspace don't do TMA and would not be looking at TMA 'sequences' which are well below their base level of FL255 anyway. After NEW is a distinct possibility since the TMA will now spot how you are going to fit in with the arrivals from the South and may ask the TAY sector to allocate you a speed.
From the South via MARGO being speeded early would be a fair cop since they start to feed in to the TMA directly and many are also valid TMA controllers so will try to start spacings early since they can see the traffic below them.
I guess you'd hate to work in the USA where speed control hundreds of miles out can be experienced regularly, but they do, to their credit, move a heck of a lot of aircraft with little airborne holding (ground delays in the conga line for departure are another thing of course !!)
To be honest, if you'd rather hold (and back to holding speed by the entry fix to keep you in the holding area, designed for 210Kts I think) when given speed control, then why not make the request ? It might save the controller a bit of work, especially if he knows you're happy to take an extra 10 minutes or so in the air without whinging about it.
The only risk is that one or two others might slip in ahead of you depending on the dynamics of your hold entry and entry level. But that's one of lifes unknowns till it happens.