**Edit: I just realized you are in Scotland. Please refer to their regulations. I only have expertise in Dairy regulatory in the US. However, the pathogen concerns and outgrowth are the same.
To be shelf stable it will have to be packed sterile no matter what temperature you "pasteurize". Dairy products are heavily regulated, and for good reason, they are highly susceptible for pathogen growth and outgrowth. Aseptic (sterile) dairy operations require minimum of 280oF for 2 seconds of pasteurization according to PMO and require sterility throughout process from pasteurization through packaging (sterile container in sterile environment).
Also, depending on the ingredient contents and level of milk protein in the finished product it could be identified as a Grade A dairy beverage and thus fall under the Pasteurized Milk Ordinance (PMO) requirements. Current PMO revision 2017 is under enforcement. See excerpt below from PMO, this is from Section 1 Definitions, GG Milk Products Definition.
"6. Products not included in Items 1-5 are Grade “A” milk products which have a minimum of 2.0% milk protein (Total Kjeldahl Nitrogen (TKN) X 6.38) and a minimum of sixty five percent (65%) by weight milk, milk product or a combination of milk products. 8 Safe and suitable (as defined in 21 CFR 130.3(d)) non-grade “A” dairy ingredients, can be utilized in the products defined in Items 1-6 when added to a level needed for a functional or technical effect, and limited by Good Manufacturing Practices (GMPs) and are either: a. Prior sanctioned or otherwise approved by FDA, or b. GRAS (generally recognized as safe), or c. An approved food additive listed in the CFR"
Edited by Ryan M., 10 July 2019 - 06:52 PM.