Wills are not usually a problem for most solicitors. Even Will writer's can do this, however, when it comes to the more advanced stages of IHT strategy within your Wills, that's a very different matter.
Inheritance tax planning, as said by others, is a special area that many solicitors and Will writes do not understand, although they may 'imply' they do. I have sat down with both solicitors and Will writers in the past and been surprised how little they know beyond the basic Will writing. My role was to help explain the 'extra' detail that was needed within the Will and I was only present at the request of the client, as they felt that my knowledge may be helpful.
I can no longer offer advice, as I have retired, but under another name, I often correct certain errors of others on a money site when people are asking questions about inheritance tax. There are many ways to save a great deal of tax and they dont cost a lot to set up.
Just be careful and take advice from someone you can trust and who has been specializing in this IHT area for some years. Only then can you possibly find the right solutions for your particular circumstances.