Extending to side can be expensive depending on roofline. Also need to know planning offset requirements. Could swap laundry and bath as follows depending on measurements and extend hall a little to make bathroom in the front wing.

Sorry thought this comment got added yesterday - extend hall to cover bathroom entry.

Thanks for these suggestions Kate.

Do you know how I can find out planning offset requirements? (Real newbie here.)

ask local council for setbacks but unless the distance from the side of the house to the side fence is at least 2m it's not worth extending sideways and very expensive for little return a you would also need to lose some of the existing kitchen to create an entry...Kate's internal changes make more sense for the bathroom improvements but you're talking about a new kitchen, bathroom and laundry for which you would need at east $40-$50,000 without any unexpected surprises and i'm wondering why the ens and laundry were arranged as shown as there seems to be enough space for a much better arrangement..i suspect that there may have been existing small rooms with internal brick walls including the wall between dining, kitchen and family that will make any improvements challenging .. there doesn't seem to be any room for expansion towards the back and also seems to be a shared driveway so..unless the house is in a fabulous area at a bargain price (including at least $50,000 for modest improvements, i would look elsewhere

Ask your local council. In vic can look at planning schemes online. Go to you council and then look at clause 56 I think