You can get birth pools for a lot less than £100 I think
Ask your midwife, if you're NHS some areas will drop off a birth pool in with your home birth kit. If not you can get them cheaper online I'm sure. I've seen them on Ebay for £10 lol, then you'd just need a liner.
It might be worth asking your midwife or asking a local doula.
I know my friend is a doula and she has a birth pool that she lets her clients use for free (or rather, included in her doula fee) but local doulas may know the cheapest places to hire or buy a birth pool & liner.
I was strongly considering it, however I keep changing my mind.
I think I might just use my bath to labour in but birth on or near my bed (if at home)
My thinking was that although waterbirth looks lovely and calm and relaxing, I don't want to be distracted afterwards having to get out & dry etc. I'd rather birth when dry so I can get straight into bed with the baby and be undisturbed for the first few hours rather than feeling the need to dry off etc.
I don't know, maybe I'll change my mind again before the birth, but at the moment I'm leaning more towards having a dry birth lol.