Do the NTAGS have to be run in the printer first before they can be changed/hacked, ie if you buy a new reel and take the ntag straight away to alter it will it work..or does it have to at least be run a while in the machine.

Also, anyone found a good alternative PLA in the uk that works well with the da vinci junior 1.0

Hope someone can advise,

Frank

No, tags can be "hacked" anytime.
If you intend to hack the tag you must do it before it goes anywhere near your printer if you have a  Mini or a Jr with firmware > 2.2.0.
The firmware in the mini and Jr (post 2.2.0) tracks the card uid and so it will not let you use previously used cards if you have "refilled" them.  Your best choice then is to swap tags.

As for PLA in the UK - these are good, cheap and offer free samples when you buy a roll.
http://shop.3dfilaprint.com/
Or use Hatchbox PLA - available from other places e.g amazon.
I have had no problems with either of these 2 - just remember to print at 210 degrees and not 190 (may need to alter tag)..

Also, anyone found a good alternative PLA in the uk that works well with the da vinci junior 1.0

Hope someone can advise,

Frank