Just been and spoke to Darryl, about "FCM - Fixed Cost Maintenance". Seems very reasonably priced in terms of paying a fixed amount monthly vs. finding the cash (~£200) for each service as and when it comes up!
I asked for a quote based on 15k/yr, and considering I've done 4k already, it worked out to be ~£16/month over 36months. Total ~£570.
We roughly worked out that if I paid for the servicies in cash each time, then it would come to about £770 in total (10k = £160, 20k = £240, 30k = £160, 40k = £160, brake fluid @ 24months = £50), but the savings might be more as we weren't sure if the 40k was a 'big' (£240) service or not, so we based it on £160 as a 'worst case' saving. ('best case' saving would be £80 more!)
Very tempted indeed to be honest, as it saves find the cash etc. and with a Direct Debit it'll come out as soon as I've been paid, so I won't really 'notice' the £££ going out.