If you're flying during the day (which I am sure you will be under VFR) and stay South of the Solway Firth and North of Kendal, there is no Controlled Airspace below FL125, which is WAY above the 5000' you are planning on operating at.
On that basis, I would personally fly VFR in the area on a QNH rather than a Standard Pressure Setting. It saves the mistake of making an error when calculating terrain clearance if you are flying using the altimeter with reference to Flight Levels.
If you need to start drifting up towards 10,000' for any reason, then would be a good time to change to 1013HPa on the subscale in case you creep up higher towards the base of the Airways. Very unlikely to be a problem though, unless there is a massive low pressure area. If you are at 10,000' on a low 970HPa, you are still going to be below the base (at 11,290' approximately or FL112).