Anything can be done but it's hard for me to believe this is a DIY project. You will need to find a way to bridge over the window with an arch or header in such a way that the load is adequately supported. Also if the wall is important to the lateral strength of the building (and an exterior solid masonry wall probably is), you need to make sure the entire opening is framed out in a way that doesn't affect the shear strength of the wall.
I see this question was asked 4 months ago (oh, and a comment added 1 month ago) so this may not matter, but the topic intrigues me. So...
Yes, there is a way to determine exactly what to do and how to determine if it will crack again. There are geotechnical engineers out there that analyze soil and sub-soil conditions. They can tell you exactly what "your" soil bearing value is and what "kind" of footing to install, (I.e.: standard spread footing, piling, etc.). However, they can't tell you how big the footings need to be...that is done by an architect or structural engineer.
They will add up all the loads in your house and decide where the loads come down on your footings and then decide if the existing footings are big enough based on the "soil conditions " provided by the Geotech Report. If they are not the right size, they can provide a design on how to fix it.
As you can imagine, this is quite expensive. An alternative to all that is to work with a REPUTABLE builder in the area and repair your walls, "fix" your footings and see how it goes. This trial and error method seems silly to me, but it probably depends on how long you're going to stay in the home.
Also, you could ask your neighbors if this occurs every year, or just once in awhile. Maybe you just repair the cracks and paint ever couple of years.
By the way, if you get the geotechnical report done, but don't follow through with the repairs, then where I live you need to disclose that when you go to sell your house. Attorneys love it when the seller does not disclose EVERYTHING.
Best Answer
This depends on how old the flat itself is, and what it's built of.
If it were actually in an 18th Century listed building, then you should definately have a full structural survey and also a specialist asbestos report as there could easily be asbestos remaining in the structure.
If it's a new development in the grounds, then treat as any other flat of the same age and structure. Management companies are not always well-run, they may not always be assertive enough at getting money to pay for maintenance, and the building may have been under-maintained for years.
Also check exactly what the listing encompasses and your responsibility for contributing to maintenance of the 18th Century building as listed building work can be very expensive - and a criminal offence if a listed building is altered or damaged without permission.