It is an old car and old cars are not reliable.Much has been said about using "specialists" but my local flea pit garage looked after all my Z series cars. £40 per hour was the labour charge. A specialist around £70. The Z3 is quite a simple car so can easily be fixed by any competant mechanic. A mobile mechanic would be able to fix the caliper problem very easily and cheaply. If you got another Z there would be no guarantee that it would not be the same. Take a deep breath, enjoy the Bank holiday weather and take your time about what you do next. And get some breakdown cover! I have a Lloyds Premier with travel insurance, home emergency, AA breakdown cover all included. Is there not a club member nearby who can help?