Thanks for all your replies . I will try to clarify - the DVD's are TEAC - even if not the best 
, I would not expect to have 5 hit the dust one after another . Below is the output from DVD Identifier program . It would appear to be DL . The CDBurnerXP also stopped at about 1/2 way .  I have an HP lPavillion laptop here - it would appear that the DVD is DL , but the DL function is not working properly . A search on Google reveals other HP laptops with this model DVD and similar problems - clear answers I don't see.  Is there some setting somewhere for DL ?  I think I will buy a disk-on-key - probably quicker and cheaper than wrecking all these DVD's anyway . I'll add this to my list of reasons why my next laptop will not be an HP .
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Unique Disc Identifier : [DVD+R-DL:CMC MAG-D03-064]
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Disc & Book Type :       [DVD+R DL] - [DVD+R DL]
Manufacturer Name :      [CMC Magnetics Corp.]
Manufacturer ID :        [CMC MAG]
Media Type ID :          [D03]
Product Revision :       [064]
Blank Disc Capacity :    [4,173,824 Sectors = 8.55 GB (7.96 GiB)]
Recording Speeds :       [2.4x , 3.3x-8x]
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** INFO : Drive = MATSHITA DVD-RAM UJ-851S - [FW 1.50] - [ATAPI]
** INFO : Write Capabilities = DVD+R DVD+R-DL DVD+RW
** INFO : Write Capabilities = DVD-R DVD-R-DL DVD-RW DVD-RAM
** INFO : Disc = [DVD+R-DL:CMC MAG-D03-064]
** INFO : Reference Speed : 1x DVD = 1385 kBps
** INFO : An Writeable Disc Is Recommended For Accurate Results
** INFO : Write Speeds (Supported By This Drive On This Disc) Listed Below
 
** INFO : GET PERFORMANCE Write Speed Descriptor(s)
Descriptor #1 =  3324 kBps ( 2.40x) - [CLV/Non-Pure CAV]
 
** INFO : MODE SENSE Write Speed Descriptor(s) [Legacy Command]
** WARNING : MODE SENSE Is Obsolete And Not Always Properly Supported
Descriptor #1 =  3324 kBps ( 2.40x) - [CLV/Non-Pure CAV]
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[ DVD Identifier V5.2.0 - 
http://DVD.Identifier.CDfreaks.com ]
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