Front sway bar bracket uses two: M8 1.25 16mm bolts. They are inexpensive ($3.50 quantity 5) and readily available as grade 8 bolts.

Given access restrictions why put in a bolt below grade 8.

The factory bolts are same size of course, but they have a 10mm head. The M8 for sale around here are all m13 hex head size.

You will need a 24 inch extension. How did I get the bolt to stay in place while I threaded it down to the bracket? I used a dab of Goop brand adhesive. It's a flexible high viscosity adhesive that'll hold things together under light stress (so if I took too long I could easily pull the wrench off). See photo.

JFT10816EP is the Jaguar part#. It was $6 + 5day wait from them. Like I said this is available in your local auto parts store.