I've included my take on it (2nd pic) but the upstairs could probably be tweaked to work a little better as a larger family bathroom would be good. You could also easily change the pantry/downstairs bathroom proportions to put in a small study too if thats more important to you than a large mud room space (first pic). Both of these have the advantage of not changing too much of the existing structure so should cost less and/or mean you can tackle redecorating those spaces at a late time when budget allows.

When concept planning a project like this I start with tracing over the plan and marking each of the more expensive elements to move - like structural walls/columns and drainage. This helps as you start with a much clearer plan. Then consider views, sunlight, movement patterns, sizes and configurations of fixtures and fittings, etc... Draw bubbles/blocks over the top of the clear plan for the different activities you'd like to accommodate - you can also cut these out of bits of paper so you can move them about and play with them until you get a configuration that you like. Hope this helps. We offer home design consultation workshops, when we visit homeowners in their homes and explore options, however, you are outside the areas we cover. You will get a much better layout if you get some professional advice and if you want this to be your forever home then it's worth getting it right. There's nothing to be lost by giving a few of your local architects a call for a chat.

Hi Paul, There is very little you need to do to reconfigure the downstairs for what you've said you want. Here is how to get everything you want: Use the current Sitting Room as a play room Knock the wall down between the current Dinning Room & Kitchen. Add large windows, ample doors, sliding doors or concertina to this area to face the garden. You can either stagger those to go with the current footprint of the house, or shave off the small back portion that protrudes, or add to level that area out (which will require moving the downstairs bathroom window). Optional : put sliding doors or pocket doors or concertina doors in between the current Lounge & new Kit - Diner space to give you self the option of opening up the lounge to views of the back garden and closing it to be separate when you want to. Keep the Lounge as a Lounge Use the current downstairs Bedroom as a Study - adding double doors out onto the garden for more light and better views. Removing the Outside Store or utilizing that space better is of course optional. Looks like a lovely home that will work how you want to live with very little structural changes overall - just some glass at the back, knocking down one wall, optionally installing some doors here and there, and configuring a new kitchen. Otherwise, it is really just about all the cosmetics and putting your own stamp on it. Best wishes & good luck!

150k is a generous budget but a 2 storey could absorb that! Loft extension about 40k minimum. A new bathroom 7-10k. New kitchen 10/15k. Structural work 10k. Redecoration 5K. New siding doors 5K. None of these are high spec prices. So you need to prioritise your needs based on your family requirements. Why do you need a downstairs loo and a separate full bathroom? Better to have a utility, loo under stairs IMO. Bathroom upstairs is a must. Do you need the third bedroom - if that is a must then the loft extension is the most cost effective way of doing this without the need to extend. Stair placement is the key consideration but your stairs may give you an option to construct this without the need to sacrifice precious space upstairs. I would merge the kitchen and loo area into an open kitchen/diner.