Barry, glad to hear the collection is finally sold.
I think the problem with many cheaper models like Brumm is the production run is not limited, so the manufacturer just keeps churning out the same models over and over. While these models were pefectly acceptable 20 years ago, they've long since been overtaken by other manufacturers. If you want to buy a 1:43 D-Type for example, aside from Brumm (@ GBP 10) you also have a superior model from Quartzo/IXO (GBP 25), an even more detailed version from Spark (GBP 40) and now the super detailed model from Autoart with openning bodywork (GBP 100).
In general, I think collectors are trading up in quality. They also value rarity which Minichamps (and their customers) learnt the hard way - their models were highly sought-after and many of their popular 1:43's would sell on the second hand market for three figures. That was until Minichamps got gready and started re-releasing their rarer models, killing the 'collectability' of their models and shot themselves in the foot in the process.
Spark/Bizarre on the other hand seemed to have learnt from this. They make a limited edition production run and do it just once. Yes, you have to pre-order the best models 12 months in advance which can be frustrating, but typically that allows them to better judge the demand for a given model and prevents large quantities ending up in the bargain basement bin on eBay (though it does still tend to happen with non-descript LM prototype DNF's).
On the other hand, some of their more desirable models are jumping 3 & 4 times in price. Look at some of the following completed ebay auctions :
Spark 1986 Porsche 956 for GBP 170 :
Spark 1964 Iso Grifo for GBP 145 :
Spark 1994 Kremer for GBP 136 :
Redline 1962 Ferrari LM Winner for GBP 133 :
Bizarre 1970 Chevron for GBP 128 :
Spark 1973 Mirage for GBP 110 :
Bizarre 1950 Frazer Nash for GBP 82 :
This is just a small selection from auctions in the last 2 months. In just my collection, I'd count at least 50 Spark/Bizarre models that now regularly sell above GBP 75, and maybe 25 that regularly sell above GBP 100. I was lucky I started collecting Le Mans cars 10 years ago, but if I was starting out collecting today there are many cars in my collection I could no longer afford.