I've just gone through this project (renovation, kitchen, new patio doors, and much more) and planning is the key. At times it will feel like you're doing 5 jobs at the same time, but it has to be done, unless you hire a full-service design & build team.
Considerations to help you plan:
- we found it took at least 3 weeks to get a few kitchen company quotes (and they vary alot). This is because of the design phase requires many iterations. And then the negotiations on pricing.
- if you're going after a German kitchen, lead time is usually like 8 weeks, so you want to get a kitchen design confirmed and deposit paid so the clock starts ticking.
- less time needed than the kitchen, but also will probably take a week or two at least to see all the suppliers and negotiate.
- if you have an existing door that you're replacing, then you need to coordinate massively. The builders will need to prepare the opening exactly to what the bifold door company needs, after they have come in and done the site survey.
- Then after ordering, it could take anything from 2-4 weeks for the manufacture before they are ready to install.
- final finishings (i.e. decorating, making good, touchups) can only be done after the kitchen and bifold are in.
- but they will need to do pre-install work. e.g. electrics, plumbing (if required), any floor levelling, and put down the first coats of paint (so its easier to do the final paint coats).
Costing - unfortunately because every project is unique, its difficult to get a "ballpark" until the actual situation is assessed. Also your size, layout, etc will be different from the next person.
Three companies I can recommend:
KDC Kitchens - was the cheapest we came across from the various German kitchen companies, and we were very happy with the final kitchen. Worktop and splashback was not competitive though, so we had to source separately (causing even more project planning complexity).
expressbifolds.co.uk - we went with them for sliding patio doors. They have their own brand range which was cheaper than the main two brands of bifold doors (which they also supplied). Happy with it, everything went smoothly.
Riga Interiors - our general builders. They did our last flat 6 years ago, and now our new home. Competitive pricing, and also above average quality of work. However, this is not a hand-off-and-go-on-holiday type of full service design and project management. You will need to be fairly hands on with the decisions and monitoring of work. Good if you're that type of disposition and would like involvement with the building project throughout. If you do get in touch, ask for Vitaliy and tell him I (Boon) sent you, as he gets quite busy at times, and a referral might be priority.