Sacked in the morning ??? (Workplace Covid issues)

You don't want to go down the unfair dismissal route, the tribunals etc are set up to side with the employer most of the time and you won't get the compo you expect. 
 Reading between the lines you're either not in a union or they're not effective. I'd suggest invoking Section 44 of the Employment Rights Act which allows you to refuse to enter an unsafe working environment.  
There is legal protection in doing this (ie a responsible employer shouldn't fire you for doing it but it doesn't sound like they're particularly responsible). At the very least your boss needs to share the risk assessment he's done that shows you would be safe. 

Agree with Rananegra says about section 44, there are template letters from the teaching unions which could give you some hints in terms of wording and approach.

other thought, have you looked at what other gas maintainer websites are saying in terms of their approach at the moment British Gas home care spring to mind and the like - https://www.britishgas.co.uk/the-source/keeping-you-safe.html

it could give a suggestion as to gaps your employer could be missing 
  

boiler services and landlords gas safety certs i thought were given a 6 month grace period. 

Good luck Gasman. Remember, they need you, as much as you need your job. 

If you feel anxious or stressed, just remember Bauer in the last minute = Instant happy feeling. 👍

Gasman said:

Brendan_O_Connell said:

This is a question and not a criticism - but if you're being careful, taking full precautions and wearing the correct PPE then what is the issue?

good question , we are very careful but not many residents are. only a few times has a resident put a mask on for example. and no matter how much PPE I use its not 100%. 
the attitude of some is shocking.

Not very helpful I know, but I live in France and when we have deliveries/visits from handymen, etc. we get an email/SMS a couple of days in advance reminding us of the appointment and the sanitary/health regulations to follow. No 1 is always “No mask, no delivery or no service”!
I can’t understand some people in the UK and their unwillingness to think of others!

The HA will have quite clear P&Ps for those staff members working in residents homes during the pandemic.

As an example, L&Q advise residents;

Our contractors will contact you to book an appointment. They’ll ask if anyone in your home is unwell, self-isolating or has any concerns about the inspection being carried out. If so, we’ll get back in touch at a later date to arrange a new appointment.

On the day of your appointment, our engineers will ask the same questions to make sure there’s been no change.

When they’re working in your home, they’ll wear protective clothing, such as face masks and gloves, and ask you to stay in another room, if possible, while they work. This is to protect them and you as they go about their work.

Once they’re done, they’ll use wipes to clean any surfaces.

We’re doing all we can not to put you at risk – our gas contractors provide daily reports on any engineers who are self-isolating or unwell. We won’t send anyone we know is unwell into your home.

Gasman said:

Little update. Im still employed but was told to get on with my job although they have agreed to change our policy of 90 day b4 certificate expiery to 60.  Talking to my work mates they agree with me 100% but dont want to be named. Guess i have to put up with it or leave. Think i will join the union for future advice. 
Many thanks again.

I think that's fair tbh. 2 months before expiry is not too out there I would imagine. I would make sure you get it in writing though as these things often come back to bite you in the future. Arse covering.

No, they will probably sack her for something else.