If anyone is interested I had this reply from the ICAO Paris office. Largely as expected but now confirmed.
"Regarding contingency procedures, there are no specific off set procedures for traffic at low levels. And although even for ATC, itīs the only procedures that we are aware and may be expecting from crews, the procedures on Ch 13 were set for the more congested airspace, like the OTS, and not for airspace below the HLA. The pilot or flight crew will make the best decision based on the situation they are at, and will probably not apply them if they are flying alone in the airspace. If they happen to have traffic below or in close proximity, than the answer might be different. But in any case, the action taken might be the natural response to the position of the other aircraft and not the application per se of the contingency procedures.
Regarding SLOP, and as itīs correctly mentioned, it applies to all levels in the NAT. Although it may seem irrelevant for traffic at those levels, and they always have the option of flying in track, itīs not uncommon for traffic to cross occasionally or fly in close proximity, even at low levels. When that happens, it might help to apply SLOP. Itīs a recommended safety feature that a lot of times is not applied as it was intended. Some operators decide that their fleet will apply a 1NM SLOP, regardless of traffic situation, when the intent is to distribute traffic as much as possible, and have pilots, for example, make a 2NM SLOP if they are close to traffic applying a 1NM or a 0 NM SLOP. So even though it might be less used at low levels, the possibility to apply it at all levels is there for pilot consideration."
Bert.