If you intend to keep the car for a while I would service it yourself and save about £100 a time, car dealerships use the stamp in the service book to blackmail people, but I have always serviced my own Hondas, kept them for a long time, done loads of miles and nothing has ever gone wrong - and a full service history doesn't make much difference to the trade in value on a 8 to 10 year old car. For 'dealer service' read 'oil and filter change' - they rarely do anything else.
£150+ at a Honda dealer is a lot to pay for an oil and filter change (I know they give you a cup of coffee and clean your car, but for £25 oil and about £8 for a genuine Honda oil filter, £18 for an air filter + less than an hour of your time it doesn't compare). You only need a 17mm spanner for drain plug, a filter wrench and remember not to overtighten either the drain plug or the filter when replacing them- the filter will leak if you overtighten, it only need to be hand tight + about 1/4 turn.
I personally change the oil twice a year and the oil and air filters once a year - if you have a set of ramps it only takes about 30 mins to do an oil change (the filter is at the front offside of engine - really easy to get to with the front of the car up on ramps). Be warned that when you take the drain plug out the hot oil will come out horizontally to start with and then the flow slackens off pretty soon, if you want to stop the oil going all over your driveway get an old Cadburys roses or biscuit tin and bodge a few holes in one end of the bottom with a screwdriver, put this on top of your normal draining can and it gives the oil a bigger area to aim at and acts as a reservoir to stop all the oil trying to get through the hole in the catcher all at once.
The best think about changing your own oil is that you know exactly what's going into the engine, Castrol magnatec semi-synthetic 5-30 or 10-40 is fine - if you are feeling generous towards your engine add some molyslip.
