I used to be the MD of a will-writing firm (so I've drafted plenty of wills in my time).
The advice I've given here on AB many times (and which I stand by now) is to get hold of a copy of this book:
Amazon.co.uk User Recommendation
(The laws on intestacy have changed since the most recent edition but everything about writing wills still holds true).
Read it, then re-read it. If you're then happy to draft your own will, do so.
At that stage you can either decide to simply sign your will in front of witnesses (leaving out the solicitor altogether) or, if you think that your draft might benefit from being reviewed by a professional, ask a solicitor to 'tidy it up' for you.