[GRASS-windows] Geolocating jpg images, supplied with jpgw World files

[Ken Mycock]

I have a series of 1km square tiles of LIDAR digital terrain model, which were 
supplied by the UK Environment Agency as jpg images, with corresponding World 
files with jpgw file extensions.  I also have vector map information from the UK 
Ordnance Survey for a much wider area, but wholly including the LIDAR coverage.

What I want to achieve seems to me be relatively simple, but I cannot work out 
how using GRASS-Win (6.4.3RC3).  I want to display the LIDAR images exactly as 
received, retaining the existing height-related colouring in their correct 
location as backgrounds to the vector map data, which I have already 
successfully imported into GRASS.

However, when I try to import the LIDAR images as raster maps (File->Import 
Raster Maps) the projection isn't recognised and the import fails.  When I turn 
off projection checking, the import runs and creates a new layer, with any 
layers below the new one disappearing across the whole extent of the vector map, 
not just the 1km square of the LIDAR, but no LIDAR data is displayed, no matter 
what display settings I vary (including turning off display of all other layers).

If I create a new location for the LIDAR data, the first tile imports and 
displays successfully, but in grey-scale only. Attempting to import a second 
adjacent LIDAR tile into this new location (redefining the region extent) blanks 
the display and neither tile is shown.

I suspect I'm missing something obvious, but can someone point me in the right 
direction please?

Ken Mycock