You do have enough Red-X. Especially with added caramel, it tends to bring some reddish hues. Carered would be best for this, but all caramel can help.

Get your tools

For recipe formulation, I really like Brewtarget. It's free, and it lets you see for yourself answers to questions like:

What would one kg brewing sugars do to a 20 liter batch of wort?

Also, it lets you select style you like, read about it, and formulate recipe that will at least keep main parameters of that style.

Malts you have that are good for reddish ale:

• Maris Otter - no colour to speak of, but solid base malt.
• Pale - looks like some generic base malt, again no colour contribution to praise or worry about. Sugar source.
• Amber - between base malt and red, will not hurt.
• Caramel Dark - Try to steep a bit of it in cold water and see colour. If it's reddish, as I expect it to be, it's good. If it's brown, don't use it for red ales.

Malts you have I would not use:

• Fawcett Halcyon Pale Malt - floor malting tends to give more browns than reds as far as I know. I might be wrong, maybe there was other factors, but I wouldn't waste it on this recipe.
• Brewing Sugars - You have enough sugar in your malt. Leave this for priming
• Black Malt - roasted malt tends to get brown. Roasted unmalted barley brings reds.

What I would do:

I would aim for red variation about Best/Premium Bitter style. Grain bill:

• Red-X 3kg
• Pale 1kg
• Maris Otter 0,5kg
• Caramel 250g

You would get red / copper colour, 1.050 OG (depending on your mash efficiency), good base for English hops if my guess is accurate.About 4.5% ABV, good for easy drinking. Not in style (nothing with malt as modern as Red X can be), but close to.

Here is Brewtarget file for this.

Adding sugar in anything but Belgian styles is not a good idea. Unless, for some reason, you want to replicate style that allowed sugar usage - but if you do, you don't have to ask.

Keep it for priming, there it's pretty good.