You definitely need a car to reach Mas Lamon, which is quite a long drive up a narrow bumpy road from Argeles. However, having driven through the rather tacky town and past the brash hotels and campsites there, you'll be pleased to be rather set back from it tucked away in the peaceful enclosure that is Mas Lamon.
We found the communication with Louise before our stay to be excellent - she replied to emails extremely quickly and helpfully, and called us before we arrived. When we did arrive, we were greeted by Frank, who was also very friendly but spoke limited English which could perhaps be a problem if your French is rusty! He gave us a quick tour of the apartment then left us to it. He had also generously left us a bottle of wine in the fridge to enjoy on our first night.
We stayed in "Canigou" which was the ground-floor apartment on the corner, looking out over the pool in one direction from the kitchen and both bedrooms and in the other the wooded grounds from the living room. The apartment was more than big enough for us, with a main bedroom with a large "super king" bed (albeit rather firm), wardrobe and large ensuite, a 2nd smaller bedroom with 2 single beds and wardrobe, a kitchen/diner with ample storage and useful leaflets and a few kids' toys left, and a living room with a sofa and sofabed, tv and a couple of small tables. Outside was a large patio area which fronted the kitchen and both bedrooms all with sliding door access, 6-seater table and chairs and 2 plastic easy chairs and a gas BBQ. The showers were nice and powerful which makes a huge difference!
We stayed in mid August in the height of a heatwave and were grateful for the electric metal shutters on the windows and ceiling fans to mitigate the heat, but it still would have been very uncomfortable to sleep had we not brought 2 of our own small fans. I agree with other reviewers that if aircon could not be installed (which would make the world of difference) at least some extra fans to move air in the height of summer would be beneficial. We tried the trick of closing the shutters during the day and opening windows after dark, but with insects also to consider it was a difficult balance between wanting to stay cool but not be bitten!
The grounds are lovely - with attractive wood and flowering bushes It is perfect for families with young children as everything is enclosed which makes you feel they are safe if you want to give them the freedom to go off and explore the play areas, boules, ping pong, football area and so on. The swimming pool is secured by a gate which my 7 year old was not quite tall enough to open alone, so is also not a significant risk.
The pool itself is larger than the photos suggest, although not enormous. It is fairly deep which was fine for us as our children can swim, but those with little ones would need to take buoyancy aids. There are plenty of reclining sunbeds around the edge with fixed umbrellas (though be aware sometimes bats like to sleep in them overnight - could be a shock when you open them!!). There is a storage chest with a few pool toys such as a ball and pool noodles. It was so nice to be able to just walk out to the pool from the flat, and we felt safe leaving the doors open.
I suspect as with most places where you are not the sole occupant, your enjoyment of a place like Mas Lamon will depend a lot on who else is staying there at the same time as you. We were extremely fortunate to find a very friendly family next door whose children ours immediately hit it off with and wanted nothing more than to spend every day playing with. It was also nice for us parents to have some new friends to share a drink with of an evening (along with the owner Frank who knew them and joined us). On the other hand a rather rowdy family group stayed a few nights we were there and rather dominated the area with loud voices in their apartment and by the pool and rowdy teenagers running and jumping around the pool which was a bit intimidating for the younger ones. However, there were only a few occasions when the pool felt busy when we overlapped with other families using it, and many times when it was empty and you could have a private swim.
Frank clearly lovingly tends and looks after his property. I would say that there were a few times this was a little intrusive as he repositioned his sprinklers to water the grass every evening which affected where the children could play (and watered the patio a few times), and another time he spent a considerable time cleaning the pool during the day with strong chemicals which meant the children couldn't play and we thought perhaps this would be better done later in the day when people were less likely to use the pool.
As other reviewers have said, the wifi at Mas Lamon is patchy at best and often had little or no signal. To be fair we found phone signal to be a problem all over the area!
On the whole, Mas Lamon was the highlight of our road trip down through France. It was mostly quiet, relaxing and we felt we could unwind. We would love to return.