Bit far out for our club unless you drive or like to add about 30 miles or more onto every ride (although the 21mph training rides start in Ashley which is only 10 mile away for you). Same with Macc Wheelers, unless you can drive out to the meeting points? In which case both clubs would cater for your ability. Additionally, there are many other clubs toward Manchester City centre and the suburbs.
However even around your local, there should be at least a few healthy clubs around the area. Most clubs will have a racing scene, some have a stronger focus than others so it is possible you contacted a very race focussed club, or they maybe even misunderstood your message to mean training rides rather than club run's etc. Even a racing club should accommodate someone with an average speed of 18mph, it is the clubs interest to help people progress and the stronger riders can help the weaker riders to progress, whether that means a stronger rider droping back to pace a weaker rider back into the group on a club ride if they get blown out, giving them a helping push up a hill (this had happened to me, I found myself going backwards in the group very quickly on a short sharp incline when I was totally spent, I then felt a hand on my lower back and suddenly found myself going forward, then it happened again, instead of letting me go out the back, 2 stronger riders had both given me a shove to help me) or giving them training tips etc.