It may not suit everyone but my personal preference when getting ready for a summer run season was to do my hill climbs as a block in the March/April time period. On the day when I would typically do an interval session I would replace this with a hill session. Always try to get a hill that is not too steep. This is not to make it easier but the incline should be such that going up it does not drastically alter your run form. Try to find a hill that is at least 300m long, use the run back down as your recovery.
Easy 10-15 minute warm up on the flat
5-6 x 60m strides on the flat
6 x circa 300m hill climb at about 80% effort
Easy 10-15 minute cool down
The two hills that I am familiar with as being good are Rose Hill Upper which is just across the river from the Mardyke just opposite the recently refurbished Red House. The other is the drive way up to the care home on the Lee Road, entrance just by the grotto.
For those who don’t want to do a hill set try an interval tempo session of 3 x 8 minutes at tempo with 3 minute easy recovery jog