After two or three cereal crops, there is every chance that grassweed populations will have increased and, where resistance is present, a large proportion of seed returned will have some resistance. Thus a well-planned rotation with an effective break crop, such as oilseed rape, provides an ideal way to tackle any build-up of resistant weeds.
Current Best Practice
You have to consider the risks extremely carefully if you are going to grow continuous wheat. It is likely that you will build up increasing resistance to herbicides and that your yields will suffer accordingly.
A rotation using either spring crops or oilseed rape is strongly recommended. For example, there is no known resistance to ASTROKerb in OSR which means that you can use this crop to dramatically reduce your resistant blackgrass seedbank.
Likewise growing spring crops allows weeds to germinate in the autumn which you can then spray off with glyphosate before drilling the spring crop. Spring cropping is however not a complete solution to grass weed problems and it is important to plan this strategy carefully.