There is no obligation to use a solicitor and a self-penned will holds just as much legality as one drawn up by a solicitor.
Couple of things though.....ensure that it is witnessed by someone who receives no benefit from the will and who has no connection with ANY beneficiary. You MUST be specific in the will and be as clear as possible to help the executor and to stop any squabbles. It is no use saying that the clock in the lounge is for our 'enry, you have to describe the clock (the longcase, bretherton clock) and the exact name of the beneficiary. It is a good idea to name the executor as well. The executor for probate can be a bank, solicitor or ANY individual. Rather interestingly I did all the probate for a relatives will. We were quoted around £8k by a solicitor....it cost me £134 and three hours of my time to do, sans solicitor ;-))) (2 hours of that was tramping to Gloucester, to swear in front of a commissioner that I was not telling any porkies ;-)) )
You can buy will templates from WHSmith as well. Asuming that the will is not complicated and you do not have a raft of shell companies in St Lucia or loads of filthy lucre entombed under the dog kennel, you will be OK.