Hi,
In answer to your questions I would suggest that unless the property is listed or is in a conservation area planning permission would not be required.
Removing a wall if it is loadbearing will require building regulations approval. You can determine whether it's load bearing by checking if there is brickwork on the first floor level above it. If there is it is. If there isn't it still may be supporting the weight of the upstairs floors so lift the carpets and see which way the floorboard run. If they run at 90 parallel to the wall it is probably load bearing as the floor joists will probably be either fixed to or resting on the brickwork. If they run at 90 degrees to the wall it probably isn't load bearing. If it isn't the wall can probably be removed for around £1000 including making good. If it is you will have to pay a chartered structural engineer to carry out a survey to determine the load bearing down on the wall so that they can specify what type and size of beam (RSJ or similar) should be inserted to support the weight when the wall is removed. If it is ok to simply rest the beam on the existing walls on a pad stone I would estimate the cost including engineers fees to be around £1500 to £2000 (of which approximately £500-600 would be design fees) so long as its only a span of 3 or 4 meters. However if there is a need to install a new spreader beam foundation this could increase considerably.
Moving the kitchen is no problem but you must units consider the other costs involved, like moving sockets and cables feeding extractors, electric oven and hob etc. and possible plastering and tiling.
I am not sure that turning the shower/toilet into one that can only be accessed from outside is a good idea. It certainly wouldn't be desirable to a potential purchaser. If this room is not required as a bathroom you might be better off to consider turning it into a utility area.
If I am to be completely honest with you I think you would really be best to try to arrange access with the estate agent and to go in with at least 2 sets of builders to get an estimate for the entire work needed to make the property how you want it. I assure you that there is almost always a lot more involved than people think.
Best of luck,
John Askem (Director)
JB Properties (Norfolk) Ltd.