One fairly easy method is to open all of your 4 photos as separate files in Photoshop (separate tabs) and then.
Take the first Photo and edit the Canvas Size by 200% in both Horizontal and Vertical directions from the top left corner.
Use the command on the menu to Tile all files horizontally or vertically so that you can see them together simultaneously.
Then Shift+Drag each photo individually into the first image. They will get added as separate layers.
You can then position each individual layer using the Arrow Tool and if you hold Shift you can constrain them to snap to the corners. Remember to be aware which Layer is active when you position using the Arrow Tool.
Also, remember once you have placed your 4 images into one composition to save it as a new PSD or PSB file (PSB if it is a very large file). You can use TIFF also but I prefer PSD because it offers some functionality and prevents you from getting confused with other TIFF files created in other programs. Remember to save with Layers so you can edit and rearrange your composition at any time.
Thank you so much for your brilliant advise & for taking the time to reply in such detail - I will try that. Thank you!
Hi. I'm glad I was able to help. The answer has been marked correct by yourself. Does that mean my suggestions worked for you?
I haven't tried it yet - I marked it as correct, as I value your detailed reply & it would stop anyone else replying to a correct answer - new to this online questions as well! I will try it tomorrow. Thank you very much again - fingers crossed.
Ok. Well, remember that your images all have to be the same size and orientation (landscape or portrait) otherwise there is extra work involved to prep your images to create a grid such as what you desire.
Thank you - I haven't printed off your replies - they are all roughly the same size - just in different colours - I will be following your advise to the T.