If you are blessed with small hands then I suggest that you disconnect the brake reservoir and CAREFULLY put to one side. Now easing your left hand into the tight space revealed BEHIND the top of the engine gently extract No.1 coil/plug cap (DO NOT DROP THE 2 FIXING NUTS). Lower an appropriate plug socket into the deep well, deftly followed with the correct extension and now attach the socket bar. Be certain you are rotating in the correct DIRECTION and watch your knuckles!! Original plugs may be VERY tight. Fit the new replacement with care; I use rubber pipe over the top of plug or the extension alone to get on the right thread. Tighten appropriately. Now, without refitting No.1 coil, work on No.2. and repeat for the rest [ I number the coils with Tippex ] I have done this twice on my 177k Jazz and I found it less tedious than the usual recommendation to remove ageing panels and wiper motors.
Make sure you have all the correct tools and leave loads of time for this fiddly task.