From experience if you have kids or anyone you want to inherit you absolutely must have a will, if the estate is worth over £325k you should also talk to a financial expert to advise on how you pass this on without them being stung for inheritance tax.
Note also you can gift as much as you like to your children and this is inheritance tax free if you live for 7 years, this is a pro rata sliding scale so if you only live 5 years after gifting they pay a percentage of the tax. Also consider putting any property in their names, as long as you trust them not to sell it from underneath you...