A locating device comprising a catheter having a catheter tube fitted at a distal end thereof with one or more inflatable insertion devices capable of being percutaneously introduced into a patient body, each inflatable insertion device comprising an inflatable element in the form of a small diameter elongate tube having a distal end and a proximal end and being operable between a collapsed condition and an inflated condition with an elongate member extending internally of the inflatable element from the distal end thereof and which is capable of being withdrawn towards the proximal end of the inflatable element to result in the distal end being withdrawn towards the proximal end internally of the inflatable element , wherein the inflatable element is a non-compliant inflatable element and pre-set to a desired generally elongate shape so as to adopt the pre-set shape when inflated, and wherein the elongate member is more flexible than the inflatable element when inflated to its pre-set desired shape, the locating device having at least one connection point at a proximal end of the catheter tube whereby inflating fluid can be conveyed to the one or more inflatable insertion devices by way of a lumen associated with the catheter tube , wherein the locating device has three inflatable insertion devices fitted at the distal end of the catheter tube evenly spaced about its circumference, each inflatable element being curved along its length and orientated so that the distal ends of the inflatable elements are directed generally towards the proximal end of the catheter tube when in the inflated condition, and wherein the inflatable elements are configured to engage and seat of the bottom of a natural heart valve leaflet. each inflatable insertion device comprising an inflatable element in the form of a small diameter elongate tube having a distal end and a proximal end and being operable between a collapsed condition and an inflated condition with an elongate member extending internally of the inflatable element from the distal end thereof and which is capable of being withdrawn towards the proximal end of the inflatable element to result in the distal end being withdrawn towards the proximal end internally of the inflatable element , wherein the inflatable element is a non-compliant inflatable element and pre-set to a desired generally elongate shape so as to adopt the pre-set shape when inflated, and wherein the elongate member is more flexible than the inflatable element when inflated to its pre-set desired shape, the locating device having at least one connection point at a proximal end of the catheter tube whereby inflating fluid can be conveyed to the one or more inflatable insertion devices by way of a lumen associated with the catheter tube , wherein the locating device has three inflatable insertion devices fitted at the distal end of the catheter tube evenly spaced about its circumference, each inflatable element being curved along its length and orientated so that the distal ends of the inflatable elements are directed generally towards the proximal end of the catheter tube when in the inflated condition, and wherein the inflatable elements are configured to engage and seat of the bottom of a natural heart valve leaflet. <EOS>