Personally I think that your starting place is budget. Consider what money is available and then prioritise what you want to do based on your situation- perhaps you need the garage most because it’s necessary for your work, perhaps you need an extra bedroom for a growing family.

Online sites can give you rough ideas of price to help work out what is possible right now. Often the ground floor extension is the most expensive as you may well end up taking on the adjoining rooms, opening up all of the space and perhaps even having a new kitchen.

Forums like this one on Houzz are great for creative input- so if you have a question about how big people think a utility room should be or a second opinion to critique your plans this is a great resource.

When you are decided about what you think you want to tackle first then you should approach the correct trade. There are building firms that specialise in loft conversions- often they have experience of planning requirements and structural engineers on speed dial and know how to arrange a party wall agreement. If you tackle the garage first then you may be building bigger and so you might consider if this would reduce how big permitted development would allow you to extend later with one of your other projects. Otherwise the garage probably just needs a general builder. And if you are looking at the ground floor extension because it likely involves the adjoining spaces you may well recruit a designer first to help plan how you will use the space as you don’t want to build a new dining room and find the old room becomes a corridor through to the new space.

I’m sure other contributors have ideas about how to find trades people. Personally I look at the planning portal of the local authority’s website to help establish which architects specialise in houses like yours, a look around your area will help establish what planners will allow, neighbours may well have recommendations for builders. And along the way this forum can help with encouragement or specific advice.

Good luck

My advice having renovated 4 houses to date would be to split it into different projects. For a dining extension you would need an architect to start. There are things like party wall agreements whether or not it falls under permitted development etc. An Architectural designer may also be able to help you with this part. You will definitely need a loft conversion specialist who could advise and build based on a wealth of experience. There are a lot rules pertinent to this extension with which you will need help. I'm not sure whether the demolition and rebuild of the garage would fall under permitted development or not? You need professional help as you are a newbie and a good architect is a great place to start. Take your time choosing one, read all the reviews and try and get an initial free consultation to see if you can work with them or not. You could also ask around locally as someone who has done similar work would know all the rules.

Thanks. Both these comments are very helpful. E.g. this idea of a maximum quota to the permitted development footprint, if I've understood correctly. Other houses near me have a) an extension b) a rebuilt garage and c) a loft conversion. Also the clear advice from experience that I need to talk to an architect. How to find one! Hmmm...

You can search Houzz by location so you could try searching projects in your area. When you find something that seems to be in a similar property and a style you like you could try to work out who the architect was, they are often credited.