moving

YANBU I thought landlords had to provide a certificate of safety and prove that the boiler was serviced by a qualified engineer. Drain cover missing is dangerous, not acceptable.

I think she could speak to the Housing Dept. at the local council. I am sure rental properties have to satisfy certain criteria. I would withold the rent, putting my reasons in writing and keeping a copy

If the letting agent won't play ball, try the CAB for advice.

Nina we have been in roughly the same situation with our letting agent. Before we moved to our current address we had a private landlord who was brilliant. If we discovered anything wrong we simply rang him. He would ask us to give him ten minutes and then within that ten minutes he would ring us back and tell us that 'Fred' or 'Jack' (or whoever) would ring us in a few minutes to book a mutually convenient time to come and do the job. The chap then rang, agreed a time - sorted.
Sadly, we had to move to be nearer our workplaces due to lack of public transport and found the ideal place but sadly it is 'managed' by an agent. We spoke to the owner and asked if she would be prepared to rent it to us privately, saving her (and us) all the ridiculous agents' fees but she explained that she is abroad a lot and needed to use an agent who could deal with any problems immediately rather than us having to wait until we could contact her - fair enough.
We were unable to use the shower for six weeks as it was seized up; we had windows that we were unable to shut because the catches were broken (good for letting the heat out!) and most recently we had a leaky roof resulting in water dripping down from above our bedroom door. On every occasion we had to continually chase the agent asking when the repairs were going to be done and each time we had the same answer - they hadn't heard back from the owner! They were waiting for the owner anyway!
Sadly, owners and agents have the upper hand which is very unfair so you have to be so careful.
One piece of advice I would give if things really get to desperation point as has happened with us in the past - NEVER EVER REFUSE TO PAY THE RENT - as if you do they can throw you out or use it against you.
I was advised by a solicitor a while ago - if needs must, pay the rent on the date it is due, then put in writing that you have paid the rent in full for the next month as it's always paid in advance.
Explain in writing that you have patiently waited for however long for the repair to be completed and that it is getting beyond a joke. Then simply say that you hope that the job will be completed by the date when the next rent payment is due, but that if it has not been rectified you are NOT refusing to pay the rent but will withhold it until the job is completed when it will be paid immediately. We had to take that action with the leaking roof and surprise surprise the roof was repaired within the fortnight.
We later had the annual inspection and I mentioned to the agent that it was just such a shame that we have to get to that point before action is taken. She tried to say that withholding rent is as bad as refusing to pay and can affect your future references but funnily enough shut up when I said we had received that advice from a solicitor and his advice would be used as mitigation if necessary!
I wish your DD all the very best as it is a real minefield and a lottery as to whether you get a good or bad agent.

As Greatnan said - keep a copy of your letter. I omitted that from my post!

Dont let the agent blame the landlord for everything. I used to own a flat that I let out and I used an agent as I was away a lot. They were good to begin with but got steadily worse when all maintenance was centralised at head office with approved contractors.

I visited the flat because I was having replacement windows and the tenant really laid into me about things that couldn't be fixed because of my delays. All these problems were new to me because the agent had not contacted me about any of them. In the end we agreed the tenant would always ring or email me everytime there was a problem then I too could chase the agent to get the problem sorted.

Quite agree FlicketyB - I am sure that half the time our agent forwards our emails to the owner and then forgets all about it until we contact them.
The owner of our place specifically told us she needed to use an agent because she often couldn't be contacted and needed the agent to act on her behalf to prevent delays if there were problems.
Funnily enough our agent is a nationwide estate agent - we viewed etc all through our local office - but when we get problems we have to contact their maintenance department some 80 odd miles away!
Seems she picked the wrong agent as they are obviously unwilling or unable to make decisions for her! Whilst I appreciate the agent can't authorise anything and everything without consulting the owner but surely when the owner has authorised them to act immediately if needed (if it is an urgent matter) they should act?

nina, in answer to your first question - yes. A tenant has the right to expect the property to be in a reasonable state of repair.
This link tells you more about tenants' rights and landlords' responsibilities.