Fleecewife has posted while I've been typing and I would agree with everything she says, especially about practicising with some lambs to fatten first before getting some to breed from.
The other thing I'd add about Shetlands is that, as far as I can see from the folks around me that have some, when crossed with a Texel, you get a perfectly acceptable fat or store lamb, often a pair of them, worth maybe 75-80% what ones out of a mule would be and probably with less effort (on your part) and less expense.
* Are store lambs only good enough for finishing off, or can these be kept as 'ewes' for the next year?
The only thing I would add to what Fleecewife says is that just because lambs are being sold in the store does not necessarily mean the farmer has selected them as not suitable for breeding. Depending on the farm and how they breed and sell, it may be inconvenient to take breeders to a breeding sale and non-breeders to the store sale, for instance. But for sure, in a breeders sale you know these animals have been selected as suitable for breeding and in the store ring, unless you ask the vendor, you don't know.
Some people do get started by keeping on female store lambs and breeding from them. Some even keep female hand-reared lambs on for breeders. You maybe won't get top-class lambs from them but the advantage is you haven't paid too much for your first girls - on whom you will make your first mistakes... And when you are ready for better stock, the ewes will fetch a decent price in the fat ring.
An alternative startup approach is to find a local farmer and ask him or her to sell you some suitable lambs, either direct from the farm or for you to buy in the ring at your local auction. The big advantage here is making the connection with the farmer, who hopefully then would be able to give you advice and, if you've bought females to breed from, maybe would even get the girls tupped for you when the time comes.
* Breed type - I dont as yet have a preference but looking for good mothering qualities, and lower 'maintenance' breeds like one that is more resiliant to foot problems etc would be good -me being a novice. Do 'Jacobs' fit into this? Any onther suggestions please. Im not looking for one that produces loads of meat.
* My local auction had lots of 'mule' ewes for sale (think thats what they were!) would these be ok.
Being a newbie at it, it is perhaps advisable to get a breed that is prevalent locally - generally they'll be suited to the locale, and there'll be lots of folk to advise you, and suitable tups to borrow / take your girls to.
If mules are popular locally you could start there. They are large sheep, good mothers, produce good meat lambs when crossed to a 'terminal sire' such as a Texel or Suffolk.
The mule is the offspring of a hill ewe and a Blue-faced Leicester tup. From her mum she gets hardiness, thriftiness and survival tactics, from her dad's lines she gets prolificacy, milkiness, good wool and a friendly and biddable temperament. Good mothering comes from both sides. The balance between the friendly, biddable Leicester and the 'ornery' hill sheep varies from mule to mule... The only real downsides with mules are (a) they have a tendency to have triplets, even quads and, coupled with that, (b) they can put too much into their lambs both before and after birth, and can suffer with twin lamb disease and other metabolic problems.
If your farmers around Redditch are anything like the ones up here, they place great value on a dark, well-marked face on a mule and there are bargains to be had with light-faced ones.
* Rams/tupping - are there any hard and fast rules (apart from rams relatives). For example if I did have 'mules' what rams can/can't put to them.
The main thing to watch out for is that the ram isn't going to produce lambs too large for the ewe. Texels and Beltex rams will put large shoulders on lambs, these can be difficult for narrow ewes to push out. Horned breeds will put horn buds on the male lambs, which can make the heads large - this can be a problem with a small ewe and/or a large single male lamb.
Mules are fairly roomy sheep and as they tend to have twins are likely to have two smaller lambs rather than one large one. They should cope with any breed of tup, really. If you are breeding them as hoggs (in their first year) you want to be sure it's an easy-lambing tup. Charollais crosses are easy-lambing, get-up-and-go lambs which grow well and produce lean good carcases. There will be other breeds you can use too but that's the one I know works on mule hoggs.
It's such fun getting into sheep - enjoy looking, asking questions and learning!