Can a Tenant do the repairs the landlord will not do?
If the landlord won't do minor repairs then yes a tenant can get the work done themselves. You can then take the cost of the repairs out of your rent. But, and it’s a BIG BUT - you MUST get advice first, because you must follow a special procedure and if you don’t you will be out of pocket and may still have to pay the rent.
Firstly, the read your tenancy agreement. This will state what each parties responsibilities are towards repairs. The landlord has many repairing obligations but not for everything (see other sections).
Now, write to the landlord explaining that if the landlord doesn't do the work within a reasonable time (e.g. 14 days) you are going to do it yourself and claim back the money from the rent. Then, If the work is not done in this time, get three professional quotes for the work, preferably from recognised tradesmen, and not your mate with a toolkit.
Send the quotes to the landlord with a letter explaining that you will go ahead with the cheapest quote unless the landlord arranges for the repairs to be done within a certain time. If the landlord still ignores your requests and the work is not done in this time, arrange for the work to be done by the company or tradesperson who provided the cheapest quote. Pay for the work and send a copy of the receipt to the landlord, making sure to keep a copy yourself just incase the original doesnt reach the landlord. Ask the landlord to refund the money first. If the landlord does not refund the money, write explaining that you are going to take the money from future rent payments.
If you don't follow this procedure, you may still be liable to pay all the rent but even if you do you can still be evicted for not paying their rent even if you followed this procedure.
If you are renting through an agent write to the agent following the above procedure. They will liaise with the landlord but actually, renting through an agent normally means that the work will get done anyway.