gaining entry to property without the tenant being there

Access

My insurance now stipulates that I must make a visual inspection of my properties and keep records once every three months. I was going to send the following letter to my tenants with follow-up letters two weeks before each of the weeks concerned. Would this be enough notice for me just to go into my properties if the tenants do not let me in please.

Dear Tenant

Due to changes in the terms and conditions for property insurance it is now necessary that either myself or someone appointed by me will have to visit your home once every three months and make a quick visual inspection of each room, any cellers and easily accessible loft spaces in the property.

I will require access to the property annually in the weeks between the dates of -

5th January to the 11th January
1st March to the 7th March
1st June to the 7th June
1 September to the 7th September

Every effort will be made to make an appointment with you but notice is given here that the landlord or someone appointed by him will effect entry to the property on the last available date of each seven day period if no appointment is forthcoming

your

I was going to do the letter in larger than standard typing and mark the envelope as 'important do not destroy without reading contents'

Thank you