I've just recently made up a set of products to use on clients in various treatments. I made a body scrub, massage oil blend & a body butter/cream. Oh & a bath salt.
Strictly speaking, if you are using the products on clients, you don't need a safety assessment as this comes under the banner of 'prescribing' products to clients.
As already mentioned there are oodles of recipes on t'internet. The fragrance for my current products (as above) is a blend of essential oils that makes it smell a bit like lemon sherbet fizz & has been incredibly popular - so much so that I've got people wanting to buy some of my products. I have been advised that I can sell to existing clients without an assessment but for Jo Public to buy them then I would need it so this is something I am looking into.
I also run children's parties where they get to make their own 'smellies'. This has proven to be really popular & just lately, we've done more 'smellies' parties than pamper parties. Even my 5yr old daughter is getting a dab hand at making bath bombs, lol