Ok here goes, please take no offence and remember you are selling it now so can't present as living in it. Firstly your photographer is rubbish, get another and don't pay first. You have good room sizes and the pictures should but don't reflect that.
A floor plan is essential, double check measurements and be sure to show total outdoor and indoor space. You could also talk up the estate agent blurb a bit, it is remarkably free from descriptive flair. Feel free to edit it and ask for adjustments - make sure someone proof reads for you before submitting though because the agents may not. That looks like a luxury bathroom to me with a traditional kitchen given a contemporary twist etc etc.
I would box half of your stuff from the shelves in the sitting room and store - aim for neat well spaced books on shelves. Store both dressers and wee unit with contents off site, remove curtains and pole, push sofa back slightly to give a bigger space, put tv on pine box and put current tv stand as coffee table in middle instead. Minimise tv by getting speakers etc out of sight and if it works size wise swap tv and chair over so room seems bigger and more welcoming. Stash magazine racks, buckets, candles, logs and all extras out of sight or elsewhere. Clean up the fireplace as best you can. One way to declutter it is take everything out, clean the room and then put back only what compliments it (so it looks hotel standard!).
Kitchen - nothing on worktops but kettle, microwave and maybe toaster at a push if it is on a crumb catcher, get all the other stuff out of sight including drain rack etc. Halve the stuff on your shelves same as the bookcase. If you can then curtain w/machine and fridge spaces. Get a photo of the kitchen with the table and chairs pulled out of the way as well as with. Move microwave to (decluttered) space on top of fridge if you can to give more worktop. Clear table. Add a fruit bowl (clear glass or wood) containing orange/lemon/lime - bright colours. Clear back of door, hoist pan rack as high as possible. I would just leave the walls, they are lovely and if you paint it too neutral your units will overpower the whole room. Find a bannister solution.
Blue bedroom, lose tall shelves, stool, centre drawers and sort the curtains out. Remake bed with ironed bedding tucked tight and straight with pillows on top and maybe a cushion or two - matching throw tri-folded at foot optional. Again look up hotel rooms to copy bed presenting techniques.
Other bedrooms need presented as such - furnish, co-ordinate and lose the pinboard and plants. Use single beds if you can to show them as bigger rooms.
Bathroom is excellent, keep window wall green and paint rest bright white, do not mix magnolia with green. Hand towel rail is in an odd place, add another below it or resite it closer to sink level.
Dress your garden picture with some pretty plants - pink or red or orange - more bright colours, then try to have it framed so you see a bit of garden with the amazing view for miles in the background not a row of houses. Maybe little table and chairs by the wall (made up for two?) with a couple of planters either side so you catch the edge of the shed (but not it's foundations!) and the view will do the rest. Experiment with sunsets and see if you can get something fabulous yourself.
Go all out for the photos, pack as much as you can now and get it stored ready for moving. For showings have fresh flowers, cleaned bleached loos and fresh coffee brewing. Hide all day to day clutter in your car (including toothbrushes). It is a showroom until you sell and treat it as such. Try to leave all cupboards/wardrobes/shelves etc much less than half full to give illusion of space - you can't hide clutter - pack it and store it.
Yawn - have bored myself now - sorry for the mammoth post. OP good luck, it is worth it, I doubled my money on my last sale 