I have been ordering from RMP for years with good customer service. They tend to order in the more expensive, slow moving items (which probably includes Roboteq controllers). The trick is to look at the stock status, which is just below the price; if it is 'Available' the item is NOT in stock and will be ordered in. That could mean significant delays if the manufacturer is also out of stock.

The other thing to know about the RMP is their very expensive international postage. To get stuff to Australia cheaply, I get the RMP to send the goods to a trans-shipping company in the US using cheap local ground shipping. The trans-shipping company then sends it internationally for about half what the RMP charges.

Its very likely you can do the same in the UK; googling 'US UK shipping' gets heaps of results.