Dzug2:
I agree that the question read as if a trust will be created but (unless there are special circumstances which we don't know about) there would seem to be absolutely no reason for it.
A simple mirror will would normally (very roughly) state "I leave everything to my spouse, subject to the proviso that they survive me for a period of 30 days. Should that not be the case, I leave my estate to be distributed as follows". (As long as both wills have the same distribution, and each partner trusts the other not to write a new will after being bereaved, there should be no problems).
If a trust is required (so that the surviving partner can't 'shift the goalposts' after the death of their spouse) then the services of a solicitor are definitely needed to draft the wills, and probably to administer the trust as well. Otherwise d-i-y wills, based upon the principles laid out in this book:
Amazon.co.uk User Recommendation
should be fine. (That book is in most public libraries).
Any adult can be an executor. Perhaps there are family friends who could help?. The task of seeking and obtaining probate is usually very straightforward.
Chris