Ok I managed to find a solution somehow all by myself.
The original was a UDF and unfinalised but had 90meg free on the disc. So I wrote a 30 meg file to the disc as a dvd-rom (iso) compilation, the previous contents showed up all with a red X by them.
I carried on and burnt disc with the finalise disc option ticked, after this Nero asked about the conflicting book types and asked if I wanted to convert the disc to ISO which I said yes to. ( It then mentions writing UDF anchor types)
Nero burnt the disc and it is now accessable by any normal means, all content is fine.
The new file added is nowhere to be seen which doesnt matter it was only a 30 meg video. There was a 2.3gig single file on the disc which now brings up a read error probably due to its size not being compatible, this is ok I will just rewrite and the disc was a total loss to me before anyway
Nero still describes the disc as a UDF.
Ive no idea why this works but it did so in case anyone finds themselves in the same mess, do the same prehaps