Ultimately, only a court can decide that.
If the landlord had not done these repairs, then you could have taken him to court in order to force him to do them - but even then, you would still have been required to pay your rent.
Obviously it was not ideal for the property to made available before it was ready. However, given that everything was done within about two weeks, it comes down to whether the landlord's actions were "reasonable". He thinks they were, and so I'm afraid only a court could decide otherwise.
In the meantime, you must continue to pay your rent in full.
UPDATE: In response to OP's comment below: according to this parliamentary briefing paper:
Although there is no general obligation on landlords to ensure
properties are ‘fit for human habitation’..., local
authorities have powers to compel landlords to tackle serious health and
safety hazards.
Again, since the repairs have been done, it seems unlikely that there is anything the local council could do.
The briefing paper also points out that:
The Landlord and Tenant Act 1985 sets out implied terms in a tenancy
agreement that require landlords to let properties which are ‘fit for
human habitation’ at commencement of and throughout a tenancy.
However:
these implied terms only apply to homes under a certain level
of rent, the amount of which has not been uprated from the level set
out in the Rent Act 1957. As a result, the provisions in the 1985 Act
only apply to those paying less than £80 annual rent in London, or less
than £52 annual rent elsewhere, and are therefore effectively
obsolete.
It continues:
There are also some longstanding common law provisions in place
regarding fitness for human habitation in furnished or newly
constructed rental properties.
