Ceano-thug

Having been told that you should prune spring flowering shrubs immediately after flowering I made a start on my prostrate ceanothus. In the space of about 6 years it has become over 3 metres wide and is nearly 2 metres tall, and is trying to take over the world. 

I went in with a vengeance this morning and filled up two large garden baggy things,  taking the ends off all the flowered wood by about 30cmts and cutting right back about a metre in places so I can get down the path that it was smothering. Underneath all the greenery there is a forest of dead wood. Will it do any harm to remove all of this? It is not looking terribly attractive at the moment

Do any of you have experience of hard pruning one of these thugs - am I likely to kill it if I go really radical or are they fighters?

Whilst I love the thing when it is in flower I am not keen on all the mess it leaves behind when it drops the blossom and it is a tad dull the rest of the year. Bees love it.

There was an evergreen one hanging right over the kitchen yard wall from next door and blocking light into the kitchen. I told the neighbour that I was going to cut it and she was ok with that.

I cut it back to the wall .................. and then it died 

Well, the book says in relation to another variety of C. thrysiflorus:

Flowers in spring and early summer on the previous season's wood.

When to prune: midsummer, after flowering.

Training and pruning: After establishing, cut back longer flowered shoots by one-third to half after flowering.  For more bushy growth, trim them again lightly later in summer.  Neglected specimens are difficult to renovate, as growth does not break from older wood.