The question is, Is loyalty affected by price and of course a certain percentage is always going to be, as it is for all of us we do the same. If you had a plumber who charged you £300.00 and needed the service again a year later but a different plumber is going to charge you £250.00 naturally you will choose the cheaper one.
As you cover such a small area and flood the area with marketing material it must be inevitable that previous customers of yours are receiving the mail outs, so in effect you are getting repeat business, if not then there is a problem with some aspect of your business either in presentation or service. But again as an established business in your area if your service was so poor then word of mouth would be a factor and you would in all probability not be operating now.
General rule of thumb for marketing spend is 5% of turnover which would put you at around £200k, as your not VAT registered then clearly you are not doing anything close to this, so your marketing spend is high but so what,if its effective and sustainable then, (especially in these time and its only going to get harder) clearly in your area this is whats required to keep you running, so keep it up.
I am not sure how anyone arrives at a view that you do not have to advertise at all simply on the basis that the business is established, if that was the case Coca-Cola would cut its entire markeing budget and save a billion or two.
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