If you really want to do this, I would suggest that you subscribe.
A lot of big name newsagents only stock part works for a few issues, unless they are very popular.
Also, if the shop is charging a pound more than the Website, it makes sense to subscribe on the Website.
I would be inclined to go to WHS and actually see the quality of the models, before you subscribe. Looking at the engine casting of the JPS Lotus, it is not superfine detail. At 1:43 the models are going to be about 10-11cm long.
Also, they are planning 60 issues. That is both a lot of money, and a lot of shelf space. However, the collection might not be worth anywhere near as much when finished. I don't think part works are anywhere near as sought after collectors items, as say Hotwheels, Dinky, or Corgi cars are.
The website says, they are planning 60 issues. That does not mean that they will not discontinue half way through.
Just my thoughts.