As far as I experience (4 years EUR short-haul):
No speed restrictions/limitations ENR (or truly scarcely so).
It is possible to get just about any level you wish. Last flight out of BRU, EET 1hr 05 min, FL390 possible after some time. Yet, due to airspace structure, we are asked to descend about 80NM ahead of optimum TOD. Staying at FL300 makes negligable fuel difference.
FD
(the un-real)