There is now a wide choice in couplings, and - at last - UK manufacturers have fairly recently adopted the NEM pocket mounting which makes it easy to fit the coupler of your choice. Because it is relatively early days since the NEM pocket was adopted, there are however a fair number of models in both Bachmann's and Hornby's ranges without this useful fitting. Of the stock you have, the Bachmann wagons are likely to be so fitted. Another immediate solution to your present problem might be to buy some screw on versions of the small tension lock coupler, to replace the older type on the Hornby; these are usually readily available in model shops in a pack of ten by Bachmann. In the longer term, take the time to look at what is available. A google on Kadee should find their website: you may well be pleasantly surprised to see how things have developed while you have been away. On which note, welcome back, there is much to enjoy.