I posted below recently. I part stripped the watch and found the pallet fork and balance to be ok and working fine. So it was just the balance spring that needed replaced. The movement in question is a Rego 129. I sourced a Rego 125 Balance spring on a balance NOS from an ebay seller 'Rigthontime2014'. He was very helpfull and there was a fraction of a mm between his replacement balance and spring and the original I measured. Unfortunalty the balance spring did not fit in the regulator hole full