Yes the runway could be grooved however it is more useful when the runway in cambered and made up of marshall ashpalt so that the water runs off towards the hard shoulders. On a flat runway the water would not have anywhere to go. I am not sure whether SEN is cambered and also the amount of repairs that may have been carried out over the years may mean grooving is not the best option as it will damage the surface.
You may also need drainage facilities on the hard shoulders to take the water away otherwise you may get ponding in that location. which may also in turn attract birds .
Grooves tend to collect rubber especially in the TDZ areas. This lessens the braking action significantly so you will need regular maintenance surveys ( monthly griptester results) and then rubber removal which is not cheap and the specialist equipment tends to be shared between the bigger airports around london. The requirements on friction testing is laid down in CAA documentation.