I'm starting a t shirt design/printing company in a few months and looking at accepting Bitcoin as payment but I'm also struggling to work out how to tier it, do I have a fixed price ie 1 BTC or do I link it to the £10 GBP price I'll be charging and people will have to pay the fluctuating BTC price?
That's a very important question, and I'm sure a lot of people wonder that.
In gold rush era, did shovel sellers sell their shovels for 1 gold nugget or 1 USD? Most likely they just accepted both, and the gold nuggets were very cheap (plentiful). As the gold started drying up, the price in gold had to naturally drop, because people just didn't have the money for it.
The same applies here; charge in BTC if that's the economy you want to grow. You'll be forced to change your prices based on how many BTCs are floating around anyway, and you can gauge that based on the exchange rate. Perhaps fixing your price for a month or something, then lowering or raising it for the next month will give start giving the currency a hint of stability. If you think the price for 1 BTC will rise over the month, you will probably be best off undercutting the GBP at the start of the month, and get most of your sales then while it's cheap, and benefit once those BTC are worth more at the end of the month. At the end of the month, when your Tshirts might be considered expensive, you'd naturally get fewer sales, except from those who really have more BTC than they know what to do with.