Is a Sales Ledger book the same as an Accounts book - or are they different ways of recording things?

A sales ledger is one specific type of accounts book, to record sales. A full set of account books will also include a purchase ledger to record what you spend, and many others.

But for your purposes, you can "keep the books" any way you like as long as it's clear. Maybe start with one of those big multi-column cash books you can get from a stationer. Record money coming in from what you sell on the left hand page, payments (including what you spent on buying the book) on the right hand page, and use the different columns to separate out different kinds of receipts and payments. It's all there for when you need to total things up for your tax return. Separating different kinds of receipts and payments out can also make you think about budgeting - "I seem to be spending a lot on this, how can I cut down?"

It would really help to have a lesson or two from an accountant (I am one!) and you can record whatever they charge as a payment. Or find someone self-employed who can show you how they do it. You can also buy software packages to record it all on but a specifically business package will expect you to be doing accruals accounts, which you don't need to do unless you are making a LOT of money out of this.

Failing any of that, and I would recommend this anyway so you can really get to grips with it, get a copy of "Business Accounting Volume 1" by Frank Wood and work through it up to the point of doing a trial balance, about halfway through the book. It doesn't matter if it's an old cheap second-hand edition, the basics of how to keep records haven't changed. DO do the exercises so you really understand. This is an absolute classic textbook and I'd be surprised to hear of a British accountant who hasn't heard of it.