None of the SLRs, Triumph or 3 Morgan chassis'd versions, competed at Le Mans. My understanding (which is welcome to be corrected if wrong!) of the reason is that Chris Lawrence had a bad road accident which put him out of action for a lengthy spell. Upon his return to fitness he moved on to the Deep Sanderson project and the Morgan's were forgotten.
Shame as the potential top speed is so much higher than anything a +4 can achieve. With some additional lighting and optimised engine cooling it would have been a great Le Mans entry!