UKH

I often set the app to record my route just out of interest to see how far I've walked. Unless I'm just wombling round the fields it's not critical that I know my altitude. When I'm out in the hills I have a paper map and know where I am. I've noticed that the app is always exaggerating my altitude, by about 60m. Has anyone else noticed this and can it be set correctly? I've also noticed that at the end of the walk it gives you the option to save and says that the altitude information will be made more accurate.

its down to some dark magic (mathermatics) involving the differnent datum and ellipsoid models used by "paper map" and GPS devices

And there was me thinking it was to stop the Russians getting a bead on me.

Nowhere in the UK are the two datums (OSGB36 and WGS84 for those that care) that far out of alignment. Even where they are, there are plenty of corrective algorithms to fix it. (Also worth noting all modern OS maps use GNSS data anyway, so are inherently based in WGS84, which is the datum GNSSs use). 

The correction at the end for "more accurate" elevation data is because GNSS aren't that great in the Z dimension - what goes on here is that your XY track is used to extract Z values from the underlying OS DEM. 

There is some difference between the two (and especially if you're in a steep valley or city and have poor VDOP), hence the option to do a correction - but nowhere is it going to be 60m out unless something else is going on.

Yup. And the OS app ought to be reprojecting to OSGB36...

OruxMaps will show GNSS altitude and DEM altitude (if you load the SRTM DEM data...)

For the OP, I would try using another app at the same time, to see if the OS app is wrong; GPS Status, for instance, set to OSGB. It shows GNSS altitude.