The base mapping is PANTS you will need something else. There are the openstreet maps available that are free but they are updated by us so they can have errors and in some of the more remote locations the minor roads are not on them. I found some of these roads going from Ruthin over to Nannarch N.Wales.
Since then as a safety point, if you want to suddenly get the 705 to calculate the quickest route home it would be nice if it had all of the roads available, I have bought the UK SD card off Amazon only £30.
I think the 705 is an awesome piece of kit just wish I could afford the 800 and then have OS maps.
Good luck, Cheers Si