No idea specifically on redcurrant, but on general principles for cuttings:

1) You need to keep the air around the cuttings moist to reduce water loss so full sun is a very bad idea. I enclose the entire pot and cuttings in a plastic bag. Remember the leaves are pumping water out, but there are no roots to replace the lost water, so you need as little leaf as you can get away with, and try to reduce water loss as close as possible to zero.

2) cuttings take a long time. If you take them now, you shouldn't remove them from the pot until you can see roots coming out the bottom, which will be some time early next summer. So this makes 1) even more important!

3) compost needs to be moist but reasonably well drained (so as not to encourage mould), so you may need to add sharp sand to it. I do my cuttings in ordinary compost, but people who do a lot of cuttings take a lot more care over the soil.

4) "fairly deeply" is a bit shallow! My cuttings are 3-4 inches long, and I have less than an inch above the soil surface.

If you're having difficult with cuttings, it may be worth layering - take a branch of the parent bush, damage the bark a bit in one place on the underside, then peg the branch down so the damaged bit of bark is against the soil. This should generate roots. Once the roots are well established, you can cut the branch, gently dig up the new plant, and transplant it to where you want it. The advantage is that the "cutting" is still getting food and water from the parent plant while it's growing its new roots.