would replacing a head gaskit mess with the e.c.u?

I recently paid over $500 on geting my head gaskit skimed and refitted. after doing so my car just cut out whilest driving round a busy ronud about a whole 2Days later. I took the car back to the same garage and they sent the E.C.U off and told me it need to reboot the emobelizer and it would cost me a further £350 to fix. Since then ive spoke to two other machaincs and they have both said the problem with the E.C.U is down to the shoddy workman ship of the garage and that I should not only demand i dont pay a penny but also they should foot the bill to get my car reapierd as they were the one who messt up the E.U.C, dose that sound rite? if anybody knows if the garage are to blame it would be greatly appretiated if you could leave a message

Many Thanks