just done a bike ride and upon tapping the route and going into settings it claims i was doing 45 mph!! what figures should be in "update time" and "update distance" ?. do you have to change these figures depending if you are walking or cycling?

The Update Time is the frequency of recording track points but,
the Update Distance is the distance you need to have travelled before a trackpoint is recorded.

Setting the Update Distance at, say 50m, should avoid lots of spaghetti track being recorded when you stop for a while.
Setting the Update Distance at, say 100000m, stops a track being recorded (unless you do more than 100km), or you could set the Update Time to be very long.

Check your track and look at the speed profile. Move the stylus along the speed profile and see where the dot is on the map display. Was there anything strange happening there? Perhaps there was a point which was noticeably off your path due to poor reception so it suddenly dropped in a 50m leg when you actually only did 20m.

Both the Update Time and Update Distance are global settings which apply to all tracks from the time you change them.

The settings you choose depend on how much detail you want to collect on the map. I suspect that you may still see apparently high speeds as I would guess that speed is calculated every second, the frequency which the position on screen is updated. i.e. it is not an averaged speed related to logging frequency, it is an instantaneous speed.

By the way, if you want to join tracks together the update distance needs to be set to a bigger value than the distance between the ends you want to join.