Hi. Welcome to the forum. Sorry its on such a major issue.
I have no direct experience of Jazz timing chain, and not an expert but I think the Jazz engine is an 'interference ' design .Meaning that if the chain snaps or' jumps teeth ' things like valves and pistons that go out of synchronisation are quite likely to collide with each other , causing significant internal damage. High chance the engine itself would be beyond economic repair. Even just stripping and investigating the engine in the hope that there will be no internal damage beyond replacing the chain would be quite expensive, with no guarantee of success. Might be throwing good money after bad. (unlike non interference engine designs where there is usually no internal collision damage but even just replacing the chain may be an unwelcome expense )
Sorry its not good news.
Bear in mind that 173,000 miles is quite a high mileage ,more than 13,000 miles per year on average. Or an even higher annual average in its earlier years. If the previous owner only had an annual service rather than every 12000 miles there may have been occasions when a service was long over due for mileage. And as it got older the engine may have consumed oil faster than it was being topped up.
If your car is otherwise in good condition, especially for rust, one solution might be to find a similar aged Jazz with low mileage that has failed its mot due to rust or crash damaged. You could do a 'full lump' engine swop into your car , and maybe defray some of the cost by selling other parts from the donor car. You might find a small garage willing to help with such a project.