Hi and welcome Philw.
Try to only rotovate your soil once, in late autumn/winter incorporating lots of well rotted manure.
Leave the soil rough with both medium sized and small size clods so that the weather,mainly the frost can get at it , and your little unpaid army of worms can drag the muck down below the suface for you.
The soil will be weathered by the wind ,rain and frost action. This will make the soil friable (crumbly).
If you rotovate and rake it over in winter to a fine tilth, the surface will pan, That is the suface will become flat and hard on top ,but often like a pudding underneath. It will remain very wet and sticky. Then in summer it will become rock hard.
The trick is to open up the soil. Then you should wait until the soil warms up, before you walk on it ,or try to dig it up. At this time of the year most clay soil will be very wet and sticky, and you will do damage to its structure if you do mess with it.
Soil warms up around 1 degree centigrade in the spring, per week.
In spring you can rake the soil over or if its ready for working and not wet and sticky follow what your fellow lottie holders are doing. Before you plant etc.
Clay retains nutrients and water a lot better than sandy soil so it is a mixed blessing. You can heap manure on it for many years and think that you are getting nowhere, but in fact it will be improving every season.