ok I have no idea of the area or price so am just looking at the pictures. def a floor plan needed. I would get some of the pictures retaken. Perhaps showing how you could close off the conservatory (make the doors visible) as it gives people more options. I always think the photos should be in the sort of order you would walk through the house in, these seem jumbled up and without a floor plan it it just confusing. You don't walk in the front door straight into the middle of the kitchen.
Bright colours are ok as they can be changed but if you want to sell then I would neutralise the walls. Bright bedroom carpets wouldn't actually bother me if the walls were neutral. BUT I don't personally like white everywhere as it can look cold and uninviting so I would go for pale neutral shades of some sort. beiges/creams etc. So lounge would become all neutral and then maybe a rug. You seem to have 3 lounges to me, no real indication of which room does what. If one is more of a quiet reading type area then put books on a bookcase in it to give it a distinct personality, if one is more of a family room then make it look like it, doesn't have to look messy or cluttered but I am looking at it thinking - ok 3 lounges but what are they all for, they just all have a sofa/chair each. Having one more like a study/library style might help add some distinction.
I would hang some towels on the towel rail.
Kitchen wise I would do something with the table - personally it looks a little like a decorating table and some kids chairs if that makes sense. I would get a different table cloth - a fabric one, and some place mats to make it look a bit more grown up or like has been said a bigger table and chairs (wood would warm it all up a bit) might just change the focus a little. For all the bright colours in the other rooms the kitchen just looks very shiny and clinical (but lovely - you should see the kitchen WE had when we moved in, it was first on my list) The hallway along to the kitchen photo 18 looks very bare to me, a console table or something might help. I would just think, great lots of storage but nowhere to put things when lifting them in or out etc.
bedrooms - make the walls in the purple and red room neutral and it will change the focus from 'oh heck this needs repainting and recarpeting' to 'oh ok bright carpet but we could just pick up the colour with patterned curtains and bedding. (red needs about 7 coats of magnolia to cover it up completely if I remember right from when we moved house when I was a child so it would put a lot of people off IMO). In the yellow and blue room I would paint the yellow to cream or white. the blue carpet then will seem easy to live with.
Garden - hmm the bit down the bottom isn't to everyone's taste. I would get some pots and pretty plants and put them down there to soften it all. You can take them with you when you move. Something with height perhaps so tall sticky things and some lower flowers. Front garden could do with some flowers in too.
hope that doesn't seem too rude, I don't mean to but if I was looking to move then I would be looking for somewhere I could move into without needing to do too much (kitchen and bathroom are good in your house), somewhere that looks like it has been a cosy, welcoming, happy home not cold and clinical and where I can imagine living as a family hence my comments about giving identities to rooms. Your kitchen is enormous, the size lots of people dream of but it just doesn't look as inviting/exciting as it probably should and certainly could. For the purposes of selling to dress it up there are different things you could do, make one of the other spaces a dining room with a nice table and chairs so giving it identity rather than another sitting room and then get an island type thing in the kitchen that is movable. Not sure if you know what I mean but it might show the space off better. Obviously you don't want to spend a fortune if you are moving but you might be able to come up with something.