Q81: How can I tell if the workman at my door is genuine and not bogus?
It is always advisable to use a chain or peephole before answering the door to anyone that you do not know.
If there is a person claiming to be from the electricity/gas/water company then they will have official ID and if they are genuine will have no problems with you looking at it and telephoning the company to verify it if you are still not happy. Look the telephone number up yourself; do not use a telephone number they give you as you cannot be sure that it is genuine.
If you have any doubts whatsoever then do not let them in. It is better to be safe than sorry. You can always then telephone the company and make an arrangement for another day.
If it is a person who wants to carry out some work on your garden/drive/roof and they make a cold call to your house then be very wary. Before having any major work done on your house, you need at least two or three quotes from different reputable companies.
If the person gives you a price that is too good to be true then it will be. There have been cases of people carrying out the job and then demanding more money.
There are also cases of the workman offering to drive the person down to the bank to get the money, which is often at a massively inflated price.
Local council building control can advise on building contractors on an "approved list". Also Trading Standards can advise on other contractors (eg burglar alarm installers). Also trade associations often have list of "registered" businesses. Plus ask the "workman" a the door for card, website address, names and addresses of local premises where he/she has undertaken work (and contact one or two of them to verify personally).
Some people who offer to carry out such tasks are genuine but there are those that are not and will take advantage of people, mainly the vulnerable and the elderly. It is advisable not to allow any workmen to carry out any tasks in your home unless they have been personally recommended to you.