my heater in the car is only blowing slightly warm when it is put on when put on cold its ok but even after an hour of driving it is only slightly warm can you help?

Yes. Bend over forward as far as you can and kiss your $$ in thanks that anything actually works!
If that does not work try pushing the washer fluid button, there is no logical reason this would help but then why apply logic where none exists.
OK l may still be a touch bitter over a less that satisfactory ownership experience w/ a Renault.
But seriously it sounds like your thermostat is stuck open thus not allowing your cooling system to heat up sufficiently.

common problem on most renaults if u ask me .. go to ur local scrapyard and get a heater matrix .. thats what needs replacing . not very expensive ..and then either look up on the net how to fit it and where it is or get it done from a garage - a very minor quick job if u know what ur doing

Yes could be stat stuck but could be a more serious problem like a blocked heat exchanger or even a leak.

Check water levels & also check the oil filler cap to see if u have any light brown sludge, this could mean u have an internal water leak either through a head gasket or a cracked waterway.

Im presuming the gauge is reading normal, the other cause could be the very cold weather, check ur handbook if u have a winter setting on ur air intake.

Another possible is the heating control mechanism is jammed shut.

My bet its the stat, few quid from halfords & 20 minutes under the bonnet

Firstly you need to see if your thermostat is opening.

With the engine warmed up nicely, touch the rubber hose that comes off the top of your engine and goes into the radiator. If it is hot then the stat is OK, if it is cool or luke warm, the stat needs replacing.

make sure there is water in the radiator the little bottle sits at the top of the engine with MAX and MIN on.

Suspect heater matrix-
look in passenger footwell for 2 plastic pipes coming through from engine compartment. These should be VERY HOT when engine is hot; if this is the case you need a matrix.
If these pipes are less than very hot then suspect lack of water/thermostat/head gasket.