I need to get a will sorted
I thought wills start from like £49 ?
Why would you need to pay £300 for a will ?
Complexity, region, how much the solicitor wants to make per will.
A simple will can be entirely boiler plate with just the names/dates etc added in and will cost next to no time to produce, a complex will might take several meetings with the solicitor, require a lot of work to do it and will obviously cost a lot more. Then you've got location, a small firm in a sleepy village will probably charge you a lot less than a big firm in nice offices in an expensive part of the country.
My brother, father and I all did wills at the same time a few years back, as they were all basically the same just changing a few names IIRC we only got charged something like 1.5x the price of one cheap will from the firm.
IIRC there are some interesting wills that have been held up in court, including one where a farmer involved in an accident basically wrote (I think in his own blood) something like "everything to my wife" on part of the farm equipment that was killing him.
Although from what I understand, by default if you die without a will it all goes to your spouse, then children, then siblings etc.