I have received some very helpful emails from Thea Lloyd, who has been endlessly patient with my stupid questions and very generous with her time.
She has kindly sent me a link to find what she describes as a useful starter set - from the Western Saddler uk company - which is a hanger and a set of reins - costing nearly £94, before we even think about postage.
Well, if this is what they cost, then this is what they cost, but at the moment I just don't have that sort of money. I have had a look on eBay, where of course bargains are to be had - but you need to know what you're looking for. If I get something cheap but unsuitable then it's money wasted that I could have saved towards a better product - a mistake we can all make when taking up any new activity.
Can anybody advise me on how you choose a bosal online? Can you just measure up your horse, as with other bridles? What are the pitfalls to avoid?

Thank you.

A good bosal is hand made from multistrands of rawhide around a rawhide core, it has to be strong, yet pliable and non abrasive to your horses sensitive nose. A good one is handmade by craftsman.£94 is not an expensive bosal, and I would be dubious of the quality.The mecate will not be horsehair.My bosal on its own was £60, but never rubbed and moulded to the horse really well.

A great tool, I do rate them.A good one is an investment.

It needs to fit the horse closely, like a hat brim, hence you will need to dampen(not wet) the bosal and bend it to fit.If you have a western bridle all ready a bosal should fit on it without the hanger, but you may have to fashion a fiador yourself.