Ok so I have to put the maps onto a micro sd card (not via wire) before they show up on my 810?
you can transfer by a cable but it takes forever, and if its on the unit's memory it fills most of it (IIRC talkytoaster map is 500mb and 800 has 700mb memory?). It takes minutes to write to a micro SD card and the map sits on the card not slowing the device down.
Was Amazon price matching the wiggle deal?
not really - the amazon deal was genuine and not for a refurbished unit. Given Wiggle were selling refurbed 800s with mapping for £279, getting the performance bundle for £209 was always suspect.
I'm assuming the iOffer 1:50 maps will do for that unit as well?
if its a genuine Garmin map then no it won't, each will only work on one unit (ie. you'd have to buy a second ioffer map for the Etrex). If they are dubiously bootlegged, or repackaged open-source map, then yes they probably will.
Do let us know how you get on!