upkeep of property

Maintenance

my tenant is keeping my beautiful property like a tip. I was only able to visit twice as i am abroad quite a lot. When I tried to go and see she always says she is busy and that she will phone me to arrange a mutually convenient time but never phones. I sent an e mail yesterday saying i will pop in as i am going that way but her son spoke from inside the house saying he cannot open the door as his mum is not there. According to my insurance with British Gas the tenant can call them out. This is helpful when I am away. A few days ago a British Gas engineer phoned me from the property as she had called him to fix a strober light which kept going off. The engineer phoned me from there to say some one has changed some wiring or something and that electricity has to be checked every year though not compulsory and I asked if he would give a quote to put it right. He said he would but so far I have received nothing. The tenant has sent me an e mail saying the engineer has said I should never have rented it without getting it checked. If anything invalidates the insurance it would be that etc because i had earlier written to her saying the way she is keeping the house will invalidate my insurance. Now she seems to be challenging after I told her to keep the place better where as before she was saying "God Bless" and behaving as if she was very religious. Can I now gain entrance with the British Gas engineer to check it out even if she does not allowe us to because she herself has written it would invalidate the insurance?